Putting together what I have found from other posts. For those who do not have audio in Kodi 21 with Flatpak, this is workaround until the pull request to default back to pulseaudio is merged.
Override the desktop launcher by copying this modified desktop file https://pastebin.com/wFddD66H
into
Code:
~/.local/share/applications/tv.kodi.Kodi.desktopThis modifies the desktop launcher to force pulseaudio
This is the pull request btw https://github.com/xbmc/xbmc/pull/25019