What boots up almost instantly? It's supported on quite a few OSes [0], not to mention the underlying hardware. I found AdGuard's (Home) UI to be a bit more polished but it feels like it has feature parity with PiHole 5 otherwise. I tried both but stuck with PiHole since the community around it seemed more developed.

[0] https://github.com/AdguardTeam/AdGuardHome/wiki/Getting-Star...