The nimble.directory domain is returning 502, Bad gateway since a few days. At first, I thought it was transitory and didn't bother reporting it, but now it appears to be a long standing issue.
If this is an "official" resource (I'd think so since it is linked prominently under the documentation link), please bring it back up.
the nimble.directory is down quite often these days.
Maybe running the website with commands like retry could help to run automatically after crash.
Systemd service?
BUT it should not crash when it crashes it must be fixed!