UPDATE: a “new” version of the package, 6.9.1-3, has now been released. This is in effect identical to 6.9.1-1: it reverts the change from the problematic 6.9.1-2.
So a normal sudo dnf upgrade --refresh should now resolve the issue.
Historical information: the below was the temporary workaround from before 6.9.1-3 was released
If you need to downgrade, you can:
sudo dnf install fedora-repos-archive
sudo dnf config-manager setopt updates-archive.enabled=0
sudo dnf downgrade qt6-qtwayland-6.9.1-1.fc42 --enablerepo updates-archive