Might be a little overkill for what you're after, but GIMP has always been excellent for me!
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Just cannot get on with it. Have tried a few times over the years.
Had the same situation.
At some point I just got used to enough of it that it's quite functional.
I wish I could change some of the defaults, but for editing it fulfills most of my needs.
GIMP does just about everything you could ever need except basic shapes.
And color management. Useless for photo editing, stuck with 8-bit sRGB.
You might look at Digikam. It is both a photo manager but has some editing functions. Not sure what they are.
The other one people talk about is Krita. I have not used that one. I would use GIMP myself but I hear you. Kind of understood the interface but now it has changed again so I struggle.
I found pinta useful. It was once forked from paint.net when it was still open source. easy to use
Inkscape and LibreOffice Draw do all that, but they're not bitmap editors.
Not open source though.
And it's a web app which is fairly annoying. Otherwise it's pretty good.
I mostly use GIMP.
I am also enthusiast about the https://graphite.rs/ project which is working in browser (love it or hate it for that).
Krita is amazing for drawing but may be intimidating.
I like MyPaint that I use as a whiteboard. It is easy to use and convenient