Can I install the latest stable (deja dup v44) on 20.04?
I needed to replace my laptop hdd. Before it was replaced, I was able to backup important stuff to my unraid server via Backup gui. The laptop had been running 20.04 lts.
When the new drive came in, I thought I’d try 22.04 lts and used the Restore via the gui. The Backup/Restore GUI in 22.04 was so much better than the version in 20.04. I’ve gone back to 20.04 due to stability issues (not at all related to deja dup) but would love to use the better gui.
Can I install the latest stable (deja dup v44) on 20.04?
No: Deja Dup v44 depends upon newer dependencies than Ubuntu 20.04 provides.
Specifically, as @guiverc pointed out, your 20.04 versions of libc5 and libgtk are too old for Deja Dup v44.
Generally, software provided by deb packages has only limited (or no) compatibility with a different release of Ubuntu. Always use the version that is built for your release.