Minecraft support has admitted that there is a know bug affecting servers. The email text reads:

Hello, 
As of update 1.19.10, it is a known but temporary issue for players to receive "an error has occurred" after attempting to join a Server, even if it is successful.
Based on the information you have provided, please check our bug reports for similar issues or submit your own so that a developer can take a look.
Once you’ve made your report, please check back in from time to time for a potential solution.