It is clear from Nevi'im (as well as modern archaeology) that the ancient Israelites practiced not only monolatry, but full fledged polytheistic idolatry until the exile / 2nd temple era. The only question is whether there are parts of the bible itself that support monolatry I.E. the notion that other Gods exist but that they are not to be worshiped. According to traditional rabbinic Judaism & Christianity, the answer is obviously no; according to modern academic biblical scholars, the answer is yes.
Polytheism from Moses to the Babylonian exile / 2nd temple period
Right from the start, according to the narrative in Exodus & Deuteronomy, 40 days after the Israelites received the 10 commandments, they already made a golden calf to worship. Moses got them back on track, but not for long. Right after Joshua (who lead Israel following Moses) died we find the following:
...Joshua son of Nun, the servant of the LORD, died at the age of one
hundred and ten years... And all that generation were likewise
gathered to their fathers. Another generation arose after them, which
did not know YHWH or the deeds that He had done for Israel... They
forsook the LORD and worshiped Baal and the Ashtaroth...
This continues constantly throughout Neveim. Even during times that there seems to be improvement, like after Solomon built the first temple, we find that in 1Kings chapter 11, Solomon's hundreds of wives, "הטו את־לבבו אחרי אלהים אחרים ולא־היה לבבו שלם עם־יהוה אלהיו" - "turned his heart after other gods, and he was not as wholeheartedly devoted to the LORD his God" and he built places of worship for them. That this is said about one of the greatest leaders at what should have been the peak period in Israelite history, gives an indication of how rampant this was.
Throughout the 1st temple period, kings promoted worship of other Gods, while Prophets rallied against it. There were kings like Hezekiah & Josiah that tried to institute reform, but they were followed by kings who served other Gods. Ultimately, according to the Talmude (Yoma 9b), Avodah Zarah was one of three causes for the destruction of the 1st temple (587 BCE).
It was following the exile that polytheism declined and was replaced by monotheism. For more on this, see https://en.wikipedia.org/wiki/Origins_of_Judaism#Second_Temple_Judaism
Monolatry in the Torah
The only question is whether there are parts of the bible itself that support monolatry I.E. the notion that other Gods exist but that they are not to be worshiped. According to traditional rabbinic Judaism & Christianity, the answer is obviously no; according to modern academic biblical scholars, the answer is yes:
"Most scholars whose work focuses on Israelite religion recognize that
the Hebrew Bible contains a number of references assuming and even
affirming the existence of other gods. As a corollary to this
observation, scholars also frequently assert that no explicit denial
of the existence of other gods occurs until the time of Deutero-Isaiah
and thereafter (6th century b.c.e.) in a presumed campaign by zealous
scribes to expunge such references from the sacred text. Even the
Shema and the first commandment do not consign the other gods to
fantasy, since the demand is made that no other gods should be
worshipped. The data apparently informs us that Israelite religion
evolved from polytheism to henotheistic monolatry to monotheism." [emphasis added]
Here I will list some verses that would seem to reflect this notion of there being other Gods. Rabbinic Judaism & Christianity find various ways of explaining/interpreting these verses in a way that is compatible with monotheism, most commonly by understanding the word "Elohim", which usually means "God" or "Gods", to mean either false gods, angles, or judges.
First are some verses where God seems to be consulting other divine beings and using the word "us". Traditional rabbinic Judaism explains that God was just showing humility:
ויאמר אלהים נעשה אדם בצלמנו כדמותנו - בראשית א׳
And God [Elohim] said, “Let us make man in our image, after our likeness..." - Genesis 1:26
ויאמר יהוה אלהים הן האדם היה כאחד ממנו לדעת טוב ורע ועתה פן־ישלח ידו
ולקח גם מעץ החיים ואכל וחי לעלם - בראשית ג׳
And the LORD [YHWH] God [Elohim] said, “Now that the man has become like one of us, knowing good and bad, what if he should stretch out his hand and take also from the tree of life and eat, and live forever!” - Genesis 3:22
[In these and the following group of verses we also see what seems to be similar to the ancient near eastern notion of a sort of God-human continuum where men & Gods can becomes more/less Godly/human. An example of this in the ANE would be, Gilgamesh who was two-thirds god and one-third man]
Next, we have some references to בני אל(ה)ים - sons of El(oh)im:
Before getting to the verses, I want to mention a bit about how the term was used in the Ancient Near Est:
The term sons of God was a common term in the mythologies of the
ancient Near East for the divine offspring of a certain god or
goddess. Thus, in the Ugaritic texts, el and his consort Asherah are
clearly designated as the parents of the gods who are collectively
designated as the "seventy children of Asherah" (II Anchor Bible VI
46), "the generation [circle, family] of El," (III K III 17–19), or
the "circle of the sons of El," (2:17, 34; 107:2). Similarly, in
Babylonia, Apsu and Tiamat are the begetters of the gods, Anu is
Anshar's first-born, etc. (see J. B. Pritchard, Ancient Near Eastern
Texts Relating to the Old Testament, 61).
The term is likewise used of demigods, whether these are represented
as the offspring of god and man (Gilgamesh being depicted as
two-thirds god and one-third man), or as a kind of god incarnate, as
were the kings of Egypt, or the Phoenician Keret, a mortal hero or
king who addresses El as his Father (I K 41, 59, 76, 169) and is
called "the son of El" and "the offspring of the Beneficent and Holy
One" (II K I–II 10–11, 20, 21).
With that in mind, let us examine the verse:
ויראו בני־האלהים את־בנות האדם כי טבת הנה ויקחו להם נשים מכל אשר
בחרו... הנפלים היו בארץ בימים ההם וגם אחרי־כן אשר יבאו בני האלהים
אל־בנות האדם וילדו להם המה הגברים אשר מעולם אנשי השם
the divine beings [Sons of Elohim] saw how beautiful the daughters of men were and took wives from among those that pleased them... It was then, and later too, that the Nephilim appeared on earth—when the divine beings cohabited with the daughters of men, who bore them offspring. They were the heroes of old, the men of renown. - Genesis 6:2,4
Altho בני־האלהים could be understood as sons of judges (or other authorities), the contrast with context of the verse makes this difficult, particularly the contrast with בנות האדם - daughters of man, fit much better with sons of deities. Likely for this reason Rashi gives an alternate explanation that it refers to angles.
בני אלים הבו ליהוה כבוד ועז...
...Ascribe to YHWH, O divine beings [Sons of Els (plural of El)], ascribe to the LORD glory and strength. - Psalms 29:1
אני־אמרתי אלהים אתם ובני עליון כלכם. אכן כאדם תמותון וכאחד השרים תפלו - תהילים פ״ב
I had taken you for divine beings [Elohim], sons of the Most High, all of you; but you shall die as men do, fall like any prince. - Psalms 82:6-7
כי מי בשחק יערך ליהוה ידמה ליהוה בבני אלים - תהילים פ״ט:ז
For who in the skies can equal YHWH, can compare with YHWH among the divine beings [Sons of Els]. - Psalms 89:7
Finally, we have verses that seem to reference other Gods more directly:
ועברתי בארץ־מצרים בלילה הזה והכיתי כל־בכור בארץ מצרים מאדם ועד־בהמה
ובכל־אלהי מצרים אעשה שפטים אני יהוה
For I will go through the land of Egypt in that night, and will smite all the first-born in the land of Egypt, both man and beast; and against all the gods of Egypt I will execute judgments: I am YHWH. - Exodus 12:12
[Some commentaries explain smiting the Gods of Egypt to be referring to the physical idols of Egypt &/ the guardian angels of Egypt.]
מי־כמכה באלם יהוה... - שמות ט״ו:יא
Who is like you among the Gods, YHWH?... - Exodus 15:11
ופן־תשא עיניך השמימה וראית את־השמש ואת־הירח ואת־הכוכבים כל צבא השמים
ונדחת והשתחוית להם ועבדתם אשר חלק יהוה אלהיך אתם לכל העמים תחת
And when you look up to the sky and behold the sun and the moon and the stars, the whole heavenly host, you must not be lured into bowing down to them or serving them. These YHWH your God allotted to other peoples everywhere under heaven - Deuteronomy 4:19
[Note: The simple straightforward meaning [pashut pshat] would seem to be that YHWH allotted these heavenly hosts as Gods for other nations, but Israel is to worship only YHWH. Some traditional commentaries say that it really means he allotted them to people as a source of light. The obvious issue with this is that it doesn't really seem to fit the context so well.]
יהוה אלהיכם הוא אלהי האלהים ואדני האדנים...
...YHWH your God is the God of divine beings [Elohim], and the master of masters. - Deuteronomy 10:17
אלהים נצב בעדת־אל בקרב אלהים ישפט - תהילים פ״ב...
...God [Elohim] stands in the divine assembly [assembly of El]; among the divine beings [Elohim] He pronounces judgment. - Psalms 82:1
אין־כמוך באלהים אדני ואין כמעשיך
There is none like You among the gods [Elohim], O Lord, and there are no deeds like Yours. - Psalms 86:8
כי אל גדול יהוה ומלך גדול על־כל־אלהים - תהילים צ״ה:ג
For the LORD [YHWH] is a great God [El], the great king of all divine beings [Elohim]. Psalms 95:3
כי־אתה יהוה עליון על־כל־הארץ מאד נעלית על־כל־אלהים
For You, LORD [YHWH], are supreme over all the earth; You are exalted high above all divine beings [Elohim]. - Psalms 97:9
גדול יהוה ואדנינו מכל־אלהים...
...YHWH is great, and our Lord is greater than all Gods [Elohim]. - Psalms 135:5
Virtually all modern academic scholars agree that at least some verses reflect a period in which YHWH was the greatest of a pantheon of Gods. However, some scholars go even further arguing that we can even see a transition from a period in which YHWH wasn't even the top God:
“The author of Psalm 82 deposes the older theology, as Israel's deity
is called to assume a new role as judge of all the world. Yet at the
same time, Psalm 82, like Deut 32:8-9, preserves the outlines of the
older theology it is rejecting. From the perspective of this older
theology, Yahweh did not belong to the top tier of the pantheon.
Instead, in early Israel the god of Israel apparently belonged to the
second tier of the pantheon; he was not the presider god, but one of
his sons. This older picture, assumed in Deuteronomy and criticized in
Psalm 82, presupposes the model of roughly equal national gods for all
of the seventy nations of the world, a notion reflected also in the
Ugaritic motif of the seventy sons of El and Athirat (CAT 1.4 VI 46).
It is true that these expressions of older national theology survive
only because they could be conformed to the later monotheistic
paradigm: the figure of "the Most High" ('elyön) in Psalm 82 could be
read as a reference to Yahweh, and the Masoretic change in Deuteronomy
marks a shift to a monotheistic reading. However, analyzed not in
terms of the later monotheism but in terms of the earlier national
situation, these two passages offer an important witness to the old
monarchic period theology of the national god. In these two cases the
Bible preserves only a limited number of "snapshots" of pre-exilic
religion, not a complete "tape." Accordingly, given the later textual
editing "out" (and "down") of Israelite polytheism, the minimal
evidence the Bible does provide should be viewed probably as only the
tip of the iceberg...”
- Mark S. Smith, The Origins of Biblical Monotheism: Israel’s Polytheistic Background and the Ugaritic Texts (Oxford: Oxford University Press, 2003), 157