Pinta served me well, but on modern distributions it's become unstable. I've resorted to GIMP and Photopea these days.

I'm jealous of the image editor built into SerenityOS (PixelPaint). It's getting awfully close to everything I want out of an image editor, but I'm not brave enough to try to port a Serenity application to Linux.

Pinta works just fine as a flatpak. Have you tried that?

It seems to be a lot more stable as a Flatpak! Too bad Flatpak is messed up on my system, but now I have a reason to fix it!