ubuntu -> kali -> lubuntu -> debian -> rhel -> arch -> gentoo + alpine -> alpine (-> openbsd + freebsd)
I consider things not in brackets 100/100 trashes (alpine is 1/2, gentoo is 3/4), in experience (because they don't help me to learn anything, I'd take openbsd on platform that X11 support is broken, for example Alpha, than anything not in brackets on amd64. Of course, that should be a personal machine for learning.)
What a lack of documentation. On BSDs we didn't suffer that.
BSD is an operating system. It diverged into FreeBSD, NetBSD and OpenBSD.