Paint.Net on Windows. Though on Windows there is Paint, that is less capable, but still no equivalent is on MacOS OOTB. (Also the drama around Paint is worth its own bashing).
I'd be interested in a similar basic tool as paint for mac and Linux (and possibly also for windows, if MS crappifies Paint, after it has tried to kill it earlier)
Pinta (essentially a reimplementation of Paint.NET) exists for MacOS as well as Linux and Windows: https://www.pinta-project.com/releases/
I want to like Pinta, but some of the load/save behaviors are just weird... not sure if I last tried the Flatpak version or not, but I've tried it on both Mac and Linux a few times... It's my go to for quick edits, but far from a fav.
There are some subtle quirks where pinta just doesn’t play ball in a way that is intuitive to a PDN aficionado.
Photopea is very close but i keep coming back to PDN either VM or RDP