Comment 21 for bug 1883040

Via this link:

http://iso.qa.ubuntu.com/qatracker/milestones/413/builds/213471/testcases

and its 'Link to the download information' you *should* be able to download the relevant mini.iso file. That way I find #621, the same as you refer to. But your results indicate that it is not upgraded from focal, so it was a dead end street :-(

-o-

Looking at your screenshots I see 'casper' mentioned

Begin: Running /scripts/casper-premount ... done.

/init: line 49 ...

If not casper maybe in a more basic 'init' system script.

I think the screenshots in comment #18 are helpful for a developer who knows better than I what should happen when booting a live drive :-)