[toast0]

I don't know about services, but MPTCP is available on Apple's OSes and out of tree patches for Linux and FreeBSD (at least I don't think it's been merged into the main tree for either of those).

Apple took a little bit too long to make it available for applications on iOS, so it didn't line up with my access to large numbers of end users and full control of the server stack, so I sadly don't have any experience with it, but it's there.

From reading the specs a while ago, I believe QUIC ended up with support for changing IPs, but not multiple IPs simultaneously, and I believe the server only can change IPs during session establishment, not with an established session.