I too came to PureOS 5 years ago with very high hopes, but then reality set in 
I eventually gave up waiting for Crimson. My experience in trying to do “the next best thing” is detailed here: PureOS Crimson (Debian 12) on Librem 15 / Librem 13 (x86-64) - #10 by JJR
I did try Pop!_OS for a while on another machine, but came back to Debian. If you intend to use Tails at any stage then familiarity with Debian would help a bit.