Although some diag tool (boot-repair: report here) run from 22.04 live USB (probably EFI) states the system is 20.04 and maybe missing an EFS partition, it never had (upgrade was run from 18.04 just after a reboot).
Only booting in recovery mode (replacing recovery with rescue in grub's linux command line) gives a ~running~ system root console.
This is because I meet some race condition in the recovery menu with the background systemctl process prompting for Enter|Ctrl+D with both want the keyboard and the screen (something like this or that).
There (rescue root console) I see none of my disk block-devices are mounted but the root (/) /dev/sda1 file system referenced by uuid in grub.
The main problem here seem to be my genuine /var that was at /dev/sdb3 not to be available.
Is there a way to have the true /var online to try dpkg --configure -a so that I don't hit dpkg: error: cannot access to administrative folder of dpkg: no such file or folder?
Please, help
[copied by hand] journalctl shows 3 very early errors (lines 188-190) I suppose irrelevant related to AMD-Vi
...
13:34:38 nux kernel: [Firmware bug]: AMD-Vi: IOAPIC[0] not in IVRS table
13:34:38 nux kernel: [Firmware bug]: AMD-Vi: No southbridge IOAPIC found
13:34:38 nux kernel: AMD-Vi: Disabling interrupt remapping
...
then far later (first related error at lines 801... just after "...Set hostname...")
...
13:34:38 nux kernel: sda: sda1
...
13:34:38 nux kernel: sdb: sdb1 sdb2 sdb3
...
13:34:38 nux kernel: sdc: sdc1
...
13:34:38 nux kernel: ip_tables...
13:34:38 nux systemd[1]: systemd 237 running in system mode. (+PAM +AUDIT +SELINUX +IMA +APPARMOR +SMACK +SYSVINIT +UTMP +LICRYPTSETUP +GCRYPT +GNUTLS +ACL +XZ +LZ4 +SECCOMP +BLKID +ELFUTILS +KMOD +IDN2 +IDN +PCRE2 default-hierarchy=hybrid)
13:34:38 nux systemd[1]: Detected architecture x86-64
13:34:38 nux systemd[1]: Set hostname to <nux>
13:34:38 nux systemd[1]: /lib/systemd/system/systemd-udevd.service:26: Executable path is not absolute: udevadm control --reload --timeout 0
13:34:38 nux systemd[1]: /lib/systemd/system/systemd-udev-trigger.service:22: Executable path is not absolute: udevadm trigger --type=subsystems --action=add
13:34:38 nux systemd[1]: /lib/systemd/system/grub-common.service:10: Executable path is not absolute: grub-editenv /boot/grub/grubenv unset recordfail
13:34:38 nux systemd[1]: /lib/systemd/system/fstrim.service:18: Unknown system call group, ignoring: @system-service
13:34:38 nux systemd[1]: /lib/systemd/system/systemd-hwdb-update.service:25: Executable path is not absolute: systemd-hwdb update
13:34:38 nux systemd[1]: /lib/systemd/system/uuidd.service:21: Executable path is not absolute: Unknown system call group, ignoring: @system-service
13:34:38 nux systemd[1]: systemd-hwdb-update.service: Cannot add dependency job, ignoring: Unit systemd-hwdb-update.service is not loaded properly: Exec format error
13:34:38 nux kernel: random: systemd: uninitilized urandom read (16 bytes read)
...
13:34:38 nux kernel: EXT4-FS (sda1): remounted. Opts: errors=remount-ro
...
13:34:38 nux systemd-journald[300]: Journal started
13:34:38 nux systemd-journald[300]: Runtime journal (/run/log/journal/c8a.....) is 8.0M max 159.9M, 144.9M free.
...
13:34:38 nux systemd[1]: Started Set the console keyboard layout.
13:34:38 nux systemd[1]: Started Dispatch Password Requests to Console Directory Watch.
13:34:38 nux systemd[1]: Reached target Local Encrypted Volumes.
13:34:38 nux systemd[1]: Reached target Local File Systems (Pre).
13:36:08 nux systemd[1]: dev-disk-by\x2duuid-ffac7b81\x2db405\x2d480b\x2d8681\x2d107e9ef9870a.device: Job dev-disk-by\x2duuid-ffac7b81\x2db405\x2d480b\x2d8681\x2d107e9ef9870a.device/start timed out.
13:36:08 nux systemd[1]: Timed out waiting for device dev-disk-by\x2duuid-ffac7b81\x2db405\x2d480b\x2d8681\x2d107e9ef9870a.device.
13:36:08 nux systemd[1]: Dependency fail for /var.
...
13:36:08 nux systemd[1]: Starting Created Volatile Files and Directories...
13:36:08 nux systemd[1]: Started Tell Plymouth To Write Out Runtime Data.
And so on for /home, /srv & Swap. I double-checked UUID's against /etc/fstab OK.
Many thanks