Can't install ubuntu20.04 on Boxes in pureOS

Installeing Ubuntu20.04 in Boxes under pureOS results, when prompted to remove installation media and restart, to an endless succession of SQUASHFS errors. Suggestions? John

Just some minor ones:

a) Ubuntu 20.04 hasn’t released yet - beware of late fixed bugs?
b) Did you verify the SHA256 sum of your download?
c) Does the install work if you install normally i.e. just install on an external disk and boot it?