multiconnect
There are 2 repositories under multiconnect topic.
ViaVersion/ViaFabricPlus
Fabric mod to connect to EVERY Minecraft server version (Release, Beta, Alpha, Classic, Snapshots, Bedrock) with QoL fixes to the gameplay
ViaVersion/ViaProxy
Standalone proxy which allows players to join EVERY Minecraft server version (Classic, Alpha, Beta, Release, Bedrock)