tldr; It still painful.
I've just switched to Thinkpad X1 Carbon and running Fedora 30. Really missed the simple Preview app in MacOS.
Basically I just want to do the usual stuff - crop/resize photos for attaching in blog post. And then some more 'advance' stuff like embedding photo in another photo.
For crop and resize, gthumb seem to do the job.
But for embedding image, I have to resort to good old Gimp in the end. Try Krita but I don't see any improvement over Gimp in term of UX.
So to embed image in Gimp, first open the image you want to embed. Select All and then Copy. Use Selection if you only need some part of it. Then open the target image, choose the Selection tools and draw the region you want to embed the image. Go to Edit - Paste into Selection (this is the key thing). The embedded image might not really fit in the target image so you may want to resize it. Go to Layer, the embedded image will appear as new layer, select it, right click and choose Scale Layer.
And that's it.