I see several lines like the following line in the log:
dec 28 21:16:36 andra gnome-software[1392]: failed to call gs_plugin_app_install on flatpak: No such metadata object 46059fc0a5b8770aa4af90bed97538e9f2d25973b8077789c22ba6773854eff4.commit
This seems to be related to the concurrency issues we’ve verified before (the updater pruning objects it shouldn’t, like in this thread).
Can you run the following command in a terminal, and then verify if you can install Gimp again?
sudo eos-fix-ostree-repo