Hrm, I always stumble over this issue with #mosh #ssh when I'm on a train ride, that the ProxyCommand does not work with mosh. But I'd need it to be able to use a "jumphost" to connect from an IPv4 only laptop/wifi to an IPv6 only device. A pity that my issue ticket at mosh regarding this was swiftly closed: https://github.com/mobile-shell/mosh/issues/1342. Mosh would have been such a perfect fit on train rides with all these cellular dead zones in Germany.