Private message routing is, effectively, a 2-hop onion routing protocol inspired by Tor design, but with one important difference - the first (forwarding) relay is always chosen by message sender and the second (destination) - by the message recipient. In this way, neither side of the conversation can observe IP address or transport session of another.

Is private message routing only for 1:1 conversations or for group chats as well?

Edit: Also, does this effectively hide my IP from the SimpleX relay operators, when sender and receiver use the default relay servers?
It reads like it’s only effective for hiding my IP from custom relays of a sender or recipient.

This looks really nice. I think the traffic reduction by not having to send to inactive group members will be very helpful as I have found that when using simple X over tor, messages can lag like a bitch. It’s bad enough that for now I actually turned it off because there were times when I would receive like a hundred messages all at the same time from like days ago.