I am using the same PPA and Gimp version 2.10.34 except it is a kubuntu 20.04
Same as Ofnuts, both those issues "mask to selection / save selection to channel" and "invert" (I get yellow from blue as expected) are working.
I can not find any easy way to go back to Gimp 2.10.32 I tried stealing packages from other linux and get dependency errors, not unexpected. Regardless of what Ofnuts says, compiling Gimp using the package you downloaded is not for the faint hearted.
Have you tried, renaming your Gimp profile and starting Gimp to make a new default version ? Then see if the problem persists.
EDIT: Just see your post, your Gimp user profile gets changed all the time. Always worth a reset.
Same as Ofnuts, both those issues "mask to selection / save selection to channel" and "invert" (I get yellow from blue as expected) are working.
I can not find any easy way to go back to Gimp 2.10.32 I tried stealing packages from other linux and get dependency errors, not unexpected. Regardless of what Ofnuts says, compiling Gimp using the package you downloaded is not for the faint hearted.
Have you tried, renaming your Gimp profile and starting Gimp to make a new default version ? Then see if the problem persists.
EDIT: Just see your post, your Gimp user profile gets changed all the time. Always worth a reset.