I keep going back to Gimp since it's inception but, it never seems to improve to the point I find it actually usable. Haven't looked in a couple of years. One more try, I suppose...

Personally, what put me off from GIMP is how the cursor didn't line up to where my tablet pen was actually drawing. It wasn't even directly above or just a bit to the right, oh no. It drew nearly an inch to the upper left from the cursor. @.@ CSP has a three month demo, if you wanna give it a try!

Affinity Photo might work for you, YMMV