LibreWolf isn't strictly a fork of Firefox, it's a preconfigured installation that locks things down and disables anti-features. So it's strictly accurate to use the Firefox user agent, because that's what actually gets compiled.

Mozilla apparently fixed this (https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=815006) so it sounds like forks don't have that issue now?

Wasn't the issue with the Iceweasel UA purely on Debian's end, them not like or agreeing to the Firefox terms? I don't think most forks would have that issue

No, it was a trademark issue, raised by Mozilla (https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=354622) and seemingly resolved on their (Mozilla's) end (https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=815006). For what it's worth, the recent Rust trademark issue seems to be of a similar vein (and the justifications around the Firefox sound like those used in Rust).

Can you provide any evidence that the User Agent name was a trademark issue. As in the name exposed to websites. Because that is the only thing that matters here and also where everyone claims to be a variant of Mozilla for compatibility.

Thanks for clarifying!