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
GNU Cobol is interesting, but note that most COBOL running in production is using other compilers and operating systems. MicroFocus and IBM COBOL are the most popular ones. They are usually executed on IBM operating systems like z/OS or IBM i, which have a hardware a bit different from a normal PC/server.
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.
VLC ships their own codecs which is great on Windows, but a bit suboptimal on a typical Linux desktop installation since you’re probably going to have GStreamer or ffmpeg available too for the rest of the software like video editors, web browsers, etc