Does God's providence (Hashgacha Pratit) extend to all people? to all individuals of the nation of Israel? or only to righteous people (צדיקים)?
Divine providence is not limited only to people.
Divine providence is that G-d governs the existence of every single physical entity. From the smallest sub-atomic particle to the largest galaxies in outer space. Each instance, every element is only in existence because of it's life force from G-d. Reshoim included.
The question you really need to ask is if everything in existence is only existence because of the life force from G-d, how can there exist bad things, suffering, and entities that go against G-d and deny G-d's existence?
According to the shaar bitachon of Chovos Halevavos chapter 3 - all human beings including non-jews.
Four: He watches over and directs the lives of all men, He does not abandon any of them nor neglects any of them . None of their matters, small or great are hidden from Him, and no matter can distract Him from remembering another matter, as written: "Why should you say, O Jacob, and speak, O Israel, 'My way has been hidden from the L-ord, and my judgment is passed over from my G-d'?" (Yeshaya 40:27), and "Do you not know-if you have not heard-an everlasting G-d is the L-ord, the Creator of the ends of the world; He neither tires nor wearies; there is no fathoming His understanding " (Yeshaya 40:28)....)
Nevertheless, it does not mean that a wicked person can trust that God will provide for him his livelihood as written later there:
But, If one trusts in G-d and rebels against Him, how foolish is he, how weak is his intellect and his understanding! For he can see in this world that if an employer appoints a man to do something or refrain from doing something and the man disobeys the instruction, this will be the strongest factor in the employer's refusing to fulfill his side of the deal. All the more so, for one who disobeys the commandments of G-d, for which G-d Himself testified that one who trusts in Him and disobeys Him will have his hopes foiled and his trust will be considered hypocritical. Rather, he will be like that of who it is written "For what is the hope of the flatterer who deceives, when G-d casts off his soul? Will G-d hear his cry when trouble comes on him?" (Iyov 27:8-9), and "Will you steal, murder, commit adultery, swear falsely, offer up to idols, and follow other gods that you know not. And will you come and stand before Me in this house, upon which My name is called, and say, 'We are saved,' in order to commit all these abominations? Has this house upon which My name is called, become a den of thieves in your eyes? I, too, behold I have seen it, says the L-ord." (Yirmiyahu 7:9-11).
(Marpe Lenefesh commentary: Even though G-d has compassion on all His creations, including the wicked, as he explained earlier, even so, for this, one should not think that G-d will forever tolerate him, and trust that G-d will continue bestowing good to him always despite his wickedness. And even though things are going well now, there is no escape from His judgments, and eventually, when He wishes, He will choose a time and place to collect His debt (of justice). Rather it is proper for a man to endeavor to fulfill all of G-d's commandments.)
On the contrary, the most righteous people in this world often have been treated most harshly until only much later did they receive a great reward. Look for example at Hevel whose greatest reward came after he was reincarnated to become Moshe. But Kain and his seed were all destroyed except for his only remnant, because of her great compassion, who was Noah’s wife.
Following Rb Dessler...
The opposite of hashgachah peratis (Divine providence for the individual) is hashgachah klalis (Divine providence for the group).
To the extent that a person identifies themselves as a prime move in the Divine plan, they will merit hashgachah peratis. To the extent that a person does not do so, their providence will be as part of the group to which they belong.