What interpretations (sources) claim the falling of manna were not meant to be taken literally in the Exodus? It was a natural event but exaggerated like the split of the Sea of Reeds. This does not make them any less miraculous.
What do “rational” Jews (rabbis) or even midrash say regarding this?
A helpful source in this discussion is (the ever-rational) Ibn Ezra, in his second commentary to Shemot 16:13:
ירקב שם חיוי שאמר כי המן הוא הנקרא בלשון פרס: תרנגבין, ובלשון ערב: מן, ובלשון לעז: מנא. כי קושיות רבות יעמדו עליו: האחד – כי אינו יורד היום במדבר סיני, כי ההר ידוע. ואני ראיתי זה הדומה למן במלכות אלנצי״ר, והוא יורד בניסן ובאייר, לא בחדשים אחרים. ועוד: אם תשימהו לשמש לא ימס. ועוד: כי בלילה לא יבאש. ועוד: כי איננו חזק, ואין צריך שידוכנו אדם במדוכה שיעשה ממנו עוגות. ועוד: כאשר יושם בלשון ימס. ועוד: כי איננו משביע שיוליד דם, רק הוא נכנס ברפואות. ועוד: כי ביום הששי היה יורד משנה. ועוד: כי לא היה יורד בשבת. ועוד: כי יורד לכל מקום שיחנו. ועוד: כי עבר עמהם הירדן, ולא שבת עד חצי ניסן, על דרך הפשט.
Let the name of Chivi rot, as he said that the Man is that which is called in Persian “Tarnagvin”, and in Arab “Man”, and in the vernacular “Manna”, as many questions will rise over him. Firstly, it does not descend today in the Sinai desert, and the mountain is known. I saw this [substance] which is similar to Man in Al-Nasir [?], and it descends in Nissan and Iyar, not in other months. Additionally, if you put it in the sun, it does not melt. Additionally, at night it does not rot. Additionally, it is not strong, and there is no need to grind it in mortars to make cakes from it. Additionally, when it is put on the tongue it will melt. Additionally, it does not satisfy [to the point of] creating blood, it only enters medicines. Additionally, on Friday double would descend. Additionally, none would descend on Shabbat. Additionally, it would fall in every place that they camped. Additionally, it crossed the Jordan with them, and did not cease until halfway through Nissan, according to the method of Peshat.
He is no nicer in his first commentary two verses later:
ישתחקו עצמות חיוי הפושע וכל הזונים אחריו שיאמרו כי מנהג זה המן לרדת עד היום במדבר...ולא התבישו אלה...והנה איננו כאשר דמו.
May the bones of Chivi the sinner and all those who turn away following him be beaten, [since] they said that it is the practice of the Man to descend until this day in the desert… Are they not embarrassed?... And behold, it is not as they thought.
For further discussion, I would suggest reading Abarbanel (Shemot 16:14), Shadal (same location), and RDZ Hoffman (16:36), all of whom approach this topic, and all of whom would be considered "rational" (and some/all were Rabbis).
