It's really going to depend on what you mean by "other things" as to what you need from said alternative.
Is it just straight photo manipulation? If so, then Gimp is the first one that does come to my mind for that type of functionality (although I have never been a fan of it, mainly the UI), more likely then not, you'll need to know python to really script some really good functionality. There is a fork of Gimp called Glimpse (where do they come up with some of these names?) that is supposed to take it into a different direction. It's a fork of Gimp 2.10, so it is the most recent version of Gimp.
Now, if you need more painterly functionality alternative, I would suggest Krita. It has some PSD functionality, and ABR functionality as well (all of my abr files imported correctly I should say). Some people call it a Ps alternative, but I consider it more of a Corel Painter alternative. It does have HDR editing as well. In fact, it has some functions that Ps only now just got or fixin to get in the latest release.
I have no experience with Affinity products, but I've heard some really good things about them, so that is another alternative.