Always willing to give a try-out. Lubuntu 20.04, installed in a VM Default Gimp is 2.10.18 - is that the version you use.
edit: Another look.
Copy / paste / cut using menu or ctrl-c / v / x working here. I see the default clipboard is qlipper, that can save images as well as text. You could try clearing / turning that off. Turn qlipper off, seems large (sometimes small - all a bit flakey) graphic clips too much for it.
If you need a basic text only clipboard then parcellite is ok.
As Nelo wrote, some other application maybe causing the problem. Run htop, that might give some clues. screenshot. https://i.imgur.com/6FcyJRb.jpg
edit: Another look.
Quote:I open a photo. Highlight some area.Large selections, they crash Gimp,
If you need a basic text only clipboard then parcellite is ok.
As Nelo wrote, some other application maybe causing the problem. Run htop, that might give some clues. screenshot. https://i.imgur.com/6FcyJRb.jpg