This was marked as solution but the requests was about virt-manager that is a libvirt management tool and not virt-viewer.
The issue is still open on the upstream and someone started to work on it but never published it.
Created a new request here since the add of virt-viewer which is a supporting tool and not virt-manager itself hasn’t been unmarked as a Solution after a month of it having been highlighted as not a Solution to the original request:
in case you didn’t get it, nobody really use this list of request (I certainly don’t). So whether it was closed or not is really unimportant. If you want something to be flatpaked, either do it, or get someone to do it.
Just setting the expectations.
And before someone ask why this forums exist, if there was none for requests, requests would be posted everywhere else.