I really love gentoo, by being sourced-based it really offers a lot of customization and flexibility compared to other distros. Software availability is usually not a problem, there is a lot of overlays and in worst case scenario writing an ebuild is not that difficult. Unfortunately the compile time on my machine makes it unusable for myself.
In second Arch or Artix-s6, wether I need/want systemd or not. What makes arch good is clearly the huge collection of ports available on the AUR and the quality of the arch wiki (wich can work on other distros btw. If a package isn’t on the AUR, writing PKGBUILD isn’t very difficult. In the case of artix, the s6 supervision suite is a very good piece of software.
And finally on low spec hardware, I really like alpine Linux, it’s running very well on my VPS on wich I host some services. Alpine Wall is great for firewall configuration .Software availability is a bit more weak due to Musl, but I foud what I needed, also APKBUILD is very similar to PKGBUILD. Honnestly it’s been very stable in this server use-case, and l’m happy with it.