Workaround from comment #5 fixes the issue! In my case I had installed "Vice 64" and got the related error. The steps illustrated in comment #5 resolved the issue for me.
https://bugs.launchpad.net/ubuntu/+source/gnome- software/+bug/2061728/comments/5 -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2061728 Title: Flatpak Apps don't launch from GNOME Software To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gnome-software/+bug/2061728/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs