As of end-of-2023, the gtk3.22-client flatpak that we made available from flathub on March, has been installed to 140000 devices according to https://flathub.org/apps/org.freeciv.gtk322
That likely makes flathub number one freeciv distribution channel. (Though large part of that statistics is the initial adoption of the flatpak during the first two weeks it was available, that won't happen again)