Tor keeps a list of fallback directory mirrors in its source code. consensus-health flags these mirrors using the synthetic flag "FallbackDir". Could Atlas do something like this, too? (Like the Not Recommended flag?) The list is updated every 2-6 months: https://gitweb.torproject.org/tor.git/tree/src/or/fallback_dirs.inc And then parsed and included in stem in a friendlier format: https://gitweb.torproject.org/stem.git/tree/stem/descriptor/fallback_directories.cfg