First I would replace the BIOS with something like Coreboot. Then it depends on your needs. Convenience? Security? Long term viability?

Coreboot, yes, if available. Stability & security.

Security + anonymity? There are plenty of distros. Personally I like Ubuntu/PopOS for plug and play (the Windows of Linux, say hello to age verification) Tails (amnesic) QubesOS (compartmentalisation e.g. with Whonix as a VM, needs RAM and CCPU) Secureblue (Graphene of Linux, very little compatibility at this point). I'd look for something without systemd like Devuan or Arch (could be as well a derivative of Arch). So for a general mix between usability and security, I'd probably go with Nix, Arch, Mint What do others have to say? Well, maybe you also want to look at BSD. It'll have a comeback for sure.