Note: While I am trying to help I am not at present using Flatpak for anything.
https://dnf.readthedocs.io/en/latest/command_ref.html
-x , --exclude=
Exclude packages specified by <package-file-spec> from the operation.
I believe in your case you would append for each package -x package_name
Like -x lib64appstream4 -x lib64flatpak0 and so forth for each package. Or you can edit /etc/dnf/dnf.conf and add a new line:
exclude=lib64appstream4,lib64flatpak0
You need to include all packages separated by a comma.
What would be better is to solve the real problem. It looks like you are downgrading the flatpack packages, so why? To problem solve I suggest picking one system and work on that.
If you do any new installs please install Plasma6. Plasma5 is weeks from the trash bin. And OM has kept it longer than a lot of distros (or so I was told). I think latest releases of Fedora and openSuSE do not have Plasma5 at all.
Note: There is a command to downgrade packages.
$ sudo dnf downgrade manually_downloaded.rpm
You can downgrade multiple packages as long as the .rpm’s are in the same directory such as ~/Downloads.
It looks like an up to date ROME system would have these installed:
rpm -qa | grep flatpak
lib64flatpak0-1.15.10-1.x86_64
lib64flatpak-gir1.0-1.15.10-1.x86_64
flatpak-1.15.10-1.x86_64
plasma6-discover-backend-flatpak-6.1.5-1.x86_64
plasma6-flatpak-kcm-6.1.5-1.x86_64
rpm -qa | grep appstream
lib64appstream5-1.0.3-3.x86_64
Please post this issue in a new thread with a descriptive title. Trying to work on 2 separate issues in the same forum thread gets to confusing.