After my recent difficulties with being unable to boot from my LUKS partition, I received help from this forum to assist me in downgrading my non-booting Clear Linux installation. I have documented the steps I took in the hope that they might also help others. Please let me know if any of the following is inaccurate especially with regards to non-encrypted partitions.
Create a Live USB with a recent version of Clear Linux
Boot into that Live USB
Connect your WiFi
Open the program ‘Disks’
Note where your ‘boot’ partition is and click on it. Make note of the Device location listed below. For example mine is listed as /dev/sda6. You may not have a separate boot partition, you might just have a ‘root’ partition. If that is the case, skip this step.
Note where your main root filesystem is located and click on it and note it’s Device location as well. If it is LUKS encrypted, click on it and click the Unlock button to unlock it. Enter your LUKS password when asked. Now a ‘root’ partition will be visible just below the LUKs partition. Note the Device location for this ‘root’ partition. It may be a very long string of characters.
Open a Terminal
Mount your ‘root’ filesystem to the directory /mnt
sudo mount <‘root’ partition location> /mnt
Mount your ‘boot’ filesystem to the directory /mnt/boot (skip if you don’t have one)
sudo mount <‘boot’ partition location> /mnt/boot
Now downgrade to the OS version you desire
sudo swupd repair -m <version #> -S /mnt/var/lib/swupd --force --path=/mnt
When completed, reboot your system.