Let’s me to investigate… I’m using a clean machine like you, formatted ext4 branch stable, and don’t get this error. Until now I tried selecting fast compression.
regarding
mount --bind --make-slave /a /home/eggs/ovarium/filesystem.squashfs/a
I tried creating a /pippo on root, and don’t evidences result.
I discovered a problem in calamares configuration /etc/calamares/modules/packages.conf when I use --fast option, the resulting installation fail
I think I will solve this in the afternoon, it’s just a misconfigured yaml. Anyway becouse the problem arise at the end of installation, the system was installed with the presence of /pippo.
BTW: it’s nice to have finally feedback. Good sunday @linux-aarhus!