Looks like it's oly available as ports, not via pkg. However I couldn't get the sway working..
It said XDG_RUNTIME_DIR is not set...
I failed to set it up without a documentation. Anyone can point me to a FreeBSD specific documentation with sway? I am on Slim display manager
I also tried export XDG_RUNTIME_DIR=~/ but it threw bunch of red lines I can't remember now, so I forgot about it now. I still don't understand how this whole wayland thing works