I added aarch64-darwin, x86_64-unknown-dragonfly and x86_64-unknown-netbsd to Tier 3 on Platform Support · crystal-lang/crystal Wiki · GitHub since they where missing or listed as Other.
Dragonfly and NetBSD should probably be well covered and qualify for Tier 2, but I’m not sure about that. Would like some confirmation first, that stdlib specs and compiler work.