I can confirm that issue on the latest development version of Ubuntu 20, on HiDPI 15" display (3840x2160) flatpak version looks less or more correct (still not very usable) and icon size setting works. repository version has tiny icons and icon size settings does not work.
-- You received this bug notification because you are a member of Edubuntu Bugsquad, which is subscribed to gimp in Ubuntu. https://bugs.launchpad.net/bugs/1817389 Title: GIMP icon sizes small on large and huge setting To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gimp/+bug/1817389/+subscriptions _______________________________________________ Mailing list: https://launchpad.net/~edubuntu-bugs Post to : edubuntu-bugs@lists.launchpad.net Unsubscribe : https://launchpad.net/~edubuntu-bugs More help : https://help.launchpad.net/ListHelp