I just downloaded a fresh install of LibreWolf to test this and it did indeed have a stable UUID for me at 1/62E6. Better than the 1/680E6 from regular Firefox, but still upsetting. Fonts and Audio fingerprinting seems to be where a lot of the entropy is coming from... Even after I enabled some of the flags to resist font enumeration it still is stable and high entropy. I'm not sure what to do to be honest about this, it is very discouraging.

Shocking, this site assigned me a UUID and I found it listed here! https://everyuuid.com/