I am specifically thinking of planets like Coruscant which does not seem to have many natural resources at their disposal. There is a page on Power generators but it says nothing on how it generates the power. I'm wondering if there is a preferably canon answer to this.
As far as I know, there isn't a clear and unambiguous answer given in canon on this subject. A lot of Star Wars technology is essentially handwaved, a function of Star Wars being more of a fantasy series in space than a sci-fi. However, we do know some things.
High energy plasma is used for at least some power generation. The power station that we saw in the Qui-Gonn & Obi-Wan vs Maul battle in Episode I is described in detail in the book Star Wars: Complete locations. It describes it as a plasma mining facility, where Naboo's natural plasma energy is drawn up from the planetary core, refined, and either used locally or traded with other worlds.
In Legends, we heard about Hypermatter, which consists of tachyons harvested from hyperspace. The main reactors of ships and stations would accelerate hypermatter particles to 'infinite' speed, the particles would annihilate, and the resultant energy was used as power generation, thrust, and to allow jumps to hyperspace.
Fusion reactors are also mentioned in various places, mostly in Legends.