Comment 4 for bug 1914521

The steps required to re-produce are

1: full disk install Lubuntu/Xubuntu (occurred after each, 20.04.2)
2: reboot & do another install using "Install alongside"

(no changes made to disk allocation, just use defaults; details entered shouldn't matter but I use "guiverc", "Chris Guiver" & password is usually "please" for QA-test installs.. machine name used varied but usually "d755-8" for box mentioned in this report).

Two outcomes

- 98% of time successful install
- at most 2% time this failure

I'm still 99.9% this is a duplicate.. but it doesn't always occur, and when it does, it's the exact same thing as had no issues other times.

This setup is far simpler to create than https://bugs.launchpad.net/ubuntu/+source/calamares/+bug/1864787 which had a more complex partition layout. To me the outcome looked the same though.