Just wanted to add that I had serious slowness problems with FreeBSD on my RPi400 initially. E.g. the extract & install phase of pkg upgrade
was particularly painfully slow when there were many packages to upgrade. However, it now seems to work quite a lot better after I changed to a different brand of microSD card (from Samsung to SanDisk, which is what Raspian is installed on). I have no benchmarks or anything to show for this, but I read somewhere that not all microSD cards are the same with regards to performance.
I'm now tempted to try it on a proper harddrive (SSD or whatever).
I appreciate the posts about alternative hardware altogether, and that perhaps FreeBSD simply cannot run as well on RPi as Linux does. I might just try different hardware at some point. However, I want to see if I can bring it to a point where the RPi is actually usable, because I think I'm quite close to this right now.