Other options include Alpine and Slackware (the former is the base of many OCI compliant containers, it’s lighter than Debian usually).
No, Gentoo, Void and Arch are not server distributions.
FreeBSD is also pretty good, although at this point, the only real argument I have seen for the BSDs is their close-ness to Unix more than anything else. If that is something you really need, you know where to go