Alpine Linux, because it uses OpenRC and musl, it's an interesting choice a little bit different but I really like it nyself for servers.
Gentoo, the biggest source based distro, has Emerge, a very configurable package manager.
NixOS, uses the Nix programming language to install packages and configuring the system. Very powerful and breaks many conventions about Linux systems
IPv6. Lack of IPv4 addresses it's a problem, specially in poorer countries. But still lots of servers and ISPs don't support it natively. And what is worse. Lots of sysadmins don't want to learn it.