I'm on Ubuntu and mostly use debs (apt), I'll use Snaps if that's the easiest way to get an update. I use Appimages for some ephemeral stuff or when that's the only way developers release it (some 3d printing stuff). I haven't installed Flatpaks at all because it doesn't jibe with the distro overall.
Ubuntu seems to dwarf other Linux distrobutions in terms of numbers of users. Are you saying more users have Flatpak installed than have Snap installed?
The numbers of app installs for popular software available from flathub.org but sure you can use the number of supported distros as an easy base. Including Ubuntu with a few workarounds.
> Ubuntu seems to dwarf other Linux distrobutions in terms of numbers of users.
I'd ask you the same thing. Based on what figures?
> Are you saying more users have Flatpak installed than have Snap installed?
Yes until Ubuntu's Snapcraft store provide download numbers. I can almost swear they used to provide this sometime back but can't see anything like that now.
Do note that the new APIs from Google require apps to take "ownership" of the update process of another app so if you update from another app then F-Droid Basic Alpha loses its ability to automatically update it until you manually update is from F-Droid Basic Alpha.
As you'd guess from the name, it's still an alpha, but from my experience it works pretty well. Bug reports are helpful, of course :)