It depends a bit on when you did this upgrade.
In the sense that as of today the elive repositories (including Bullseye) aren't being resolved i.e found.
So your problem might just be that and hopefully "repaired" in due time.
Considering the audio was a Debian problem .... maybe my first course of action could work for you (the script line is an interpretation of that by @Thanatermesis , which I personally haven't tested).
From the first post:
So do give that a go and wait out to when the Elive repositories come up again.
On a hopefully superfluous sidenote:
As mentioned before in the Howto, upgrading to Bullseye is 'testing' and not considered stable or safe ........ so expect bugs.
