Peer-to-peer synchronisation

This address is retained for links to an earlier P2P guide. The time-specific interface description has been replaced by stable documentation:

Set up peer-to-peer synchronisation for the first device, additional-device Setup URI, approval, and two-way verification.
How peer-to-peer synchronisation works for signalling, TURN, privacy, the P2P Status pane, and automatic behaviour.
Peer-to-Peer Synchronisation Tips for connection troubleshooting.