Comment 2 for bug 1899107

In case you still have the system in place, would you mind also having a look /var/crash and if it's not empty (what I assume) attaching the content here, too?
(With "F2"
I think that if you scroll down the subiquity screen a bit, there will be an option to 'Continue' available - if so, are you able to complete the installation then?

I 'think' this could be a duplicate of LP 1893818, which happens to me mainly on LPARs, but at least on zFCP/SCSI multipath installations only.
There is the same log entry in subiquity-debug visible:
"2020-09-17 13:42:57,730 ERROR root:39 finish: subiquity/Filesystem/_probe/probe_once: FAIL: Invalid dep_id (partition-sda1) not in storage config"

But I'm waiting for an answer before I really mark this as duplicate ...