Steps to reproduce:

1. attempt to join a Minecraft server
2. disconnect
3. open a singleplayer world
4. disconnect
5. go back to the multiplayer server list

the server icon is now replaced. It is possible that it is somehow saving the singleplayer icon over an existing icon in the multiplayer list. The exact details were that these servers were running an older version of the game (1.18, 1.17) and were not online at the time but this may still affect online servers running versions 1.19 or later.