There is an upstream bug in 12.1 that keeps the 12.1 client from connecting to a 12.1 server on another machine. Reproducible: Always Steps to Reproduce: 1.start 12.1 server on machine a 2.From machine b psql -h a db Actual Results: Returns error psql: error: could not connect to server: FATAL: unsupported frontend protocol 1234.5679: server supports 2.0 to 3.0 Expected Results: Should have connected There are two patches from upstream that addresses this on both the client and the server. Applying the patches fixed the issue for me.
Created attachment 599976 [details, diff] client patch
Created attachment 599978 [details, diff] Server patch
Probably obsolete with versions 12.2/12.3 in tree?