I don’t have a Librem, but I have played with the BSD’s some.
I think you can get a FreeBSD or NetBSD qube going without too much hassle so that may be worth checking out for you.
The biggest thing I found is that while Linux has an acceptable amount of software choice for most people’s day to day use, the BSD’s have the software for some people’s day to day use.
I was personally most drawn to OpenBSD and it can be run as a desktop OS, but this is not something I recommend for most people as there is not enough software available for most people’s daily computing tasks, and even some of the software that is available isn’t quite the same.
This is just my experience with this and I do have a server running FreeBSD to test things on and my firewall is an OpenBSD firewall, but my combination Plex and NextCloud server running Debian; because, when I set it up, at least one of those couldn’t be easily made to work on *BSD.