You installed GIMP via the software center of Ubuntu and it's a snap. My condolences ..
Uninstall it, and instead install it via the official website (flatpak, berk), of via the PPA from Panda Jim over-there > https://launchpad.net/~ubuntuhandbook1/+...buntu/gimp , there is also an AppImage from Tas_mania (17) on github (I forgot the link)
Uninstall it, and instead install it via the official website (flatpak, berk), of via the PPA from Panda Jim over-there > https://launchpad.net/~ubuntuhandbook1/+...buntu/gimp , there is also an AppImage from Tas_mania (17) on github (I forgot the link)
Patrice