ZFS failure while installing 12.3-RELEASE

Greetings,

I just tried installing 12.3-RELEASE on a box that had been running Oracle
Linux-7.9, and I got all the way through the install with no problems.
I have 5 drives; 2 are identical WD 1-TB, 2 are identical WD 3-TB,
and one Crucial SSD.

The system found all the drives (including the SSD, to my surprise --
it was connected via USB cable).  I set up a basic mirror on the two WD
1-TB drives, figuring I'd do the rest of the disk setup later -- I want
a mirrored root filesystem but other things can go on the SSD.

I got into my setup menu (Intel) and asked to boot from the DVD without
changing the default boot order, which tries the disk first.  The install
went fine, but when rebooting from the drive, I saw a ZFS failure:

    Solaris: zroot/ROOT/default: can't open objset 108, error 6.

It tried again after three seconds, no joy.  Reboot into single-user
also fails, and trying rescue from the DVD only shows me the DVD itself;
I don't have a writable root partition.  I can do ls and lsdev, and I
see drives like ada0p4 and ada1p4 listed as ZFS, but I'm not sure what
to do next.  Some suggestions I've found:

    zpool status
    zfs list

Add the following to loader.conf:

    vfs.zfs.debug="1"
    boot_pause="YES"
    geom_label_load="YES"
    geom_part_gpt_load="YES"

Tell the system more specifically what to load in /boot/loader.conf:

    vfs.root.mountfrom="zfs:zroot"

I have another system running FreeBSD-11.4 (no problems) and
/boot/loader.conf contains:

    kern.geom.label.disk_ident.enable="0"
    kern.geom.label.gptid.enable="0"
    zfs_load="YES"
    accf_data_load="YES"

The last suggestions I found were

    zpool import -fR /mnt zroot
    zpool get bootfs zroot

If the "get" command didn't give me anything, try

    zpool set zroot bootfs zroot

I did the install under UEFI, and now I can't seem to get to my setup page
at all -- pressing F2 or F10 during boot doesn't work like it used to.
I'm very surprised; FreeBSD installations have always gone smoothly in
the past.

Any suggestions welcome.  Hoping I didn't somehow brick my system.

--
Karl Vogel / vogelke AT pobox DOT com / I don't speak for anyone at the moment

To make error is human.  To propagate error to
all server in automatic way is devops.           --If Borat worked in IT