As well as the package manager (and release type/schedule as mentioned in a different reply) you might want to look at the overall structure.

Does the distro use selinux or app armor (you probably want at least one)? Does it follow traditional distro structure like Ubuntu/Debian or is it weird like atomic (ex Silverblue) or declarative (ex Nixos) distro? Is it a minimalist distro (Arch is the big modern one) it maximalist (Suse)? Those kinds of things can also be informative.