I had the same gpg error after trying to rebase to F39 after updating to F40 on Bazzite (Gnome Nvidia).
I updated to F40 and it was kind of a mess. GPU performance was messed up whereas on F39 it wasn’t. Even playing Youtube videos without stuttering / artifacts was no longer possible. I was getting massive screen tearing when gaming (like on crack type of screen tearing). Also, 2 of my printers stopped working, and I no longer was able to mount my two ntfs windows drives. I was getting permissions errors when trying to mount.
When I figured “hey I’m supposed to be able to just back out right?”, I tried to rebase to F39 only to get the GPG error (same as above).
I ended up having to turn off GPG in several of the etc/yum.d.repos rpmfusion files in order to get it to rebase. Somethings not right guys… This was on a roughly one or two week old installation. I realize that I would be advised not to turn off gpg, but when you are as new / dumb as I am, you just want to get it done and move on.
