I’ve been messing around with Krita, and it’s pretty decent alternative to PS. It does have its quirks, though, like the layer clipping mask system is super weird and I don’t like it. You have to group layers if you want clipping mask properties, but the lowest layer will affect how it works. So, if you have a background with a character and want to limit your strokes to the character, you must have the character layers in a group or else the lowest layer (BG) will be the “limits” of the strokes, if that makes sense. It confused the crap out of me when I first did it. Whereas in PS, right click, make clipping mask, and done. There are some hotkeys I like in Krita than in PS and then some frustrations with my grokked PS hotkeys that don’t translate to Krita. Overall, I think it’s a decent alternative to PS, just quirky. There are other alternatives out there, too, but I can’t speak for those.
Remember, the tool doesn’t matter as much as what you can make with the tool. There are some excellent artists out there that only use a couple of brushes in a drawing software. Give each software a try, and see what works best for you. Sure, you’ll have to translate some things, but that’ll give you an edge when helping somebody else with similar problems.