Currently Facter 4 is locked to ruby 2 (~> 2.3) which does not allow installation on Ruby 3.
Projects that depend of Facter and are installed on Ruby 3, will fetch Facter 2.5.7
Merged in https://github.com/puppetlabs/facter/commit/30a03ac421c212d6742a091622258a6fe05439e9