Kirta is a very good program. I've been using Paint Studio Paint Ex which you can usually find on sale, and which is not a subscription, it's very pleasant to use and has lots of resources available. They offer a three month trail and a cheaper version as well. That said, I think you should just use Krita a bit more and get deeper into it, to see whether or not you like it. For map specific programs I think you may just have to break down and use a windows partition, that Humble Bumble deal sounds like it might be worth while.