https://bugs.launchpad.net/watcher-dashboard/+bug/2109608 has been completed
In the previous sprint, however, I intentionally deferred dropping 3.9 support in bug fix to allow the centos 10 master jobs to be developed.

now that they have been running for some time an looks to be stable its time to
block installation on 3.9 as this has been untested for some time now.