A couple decades ago I did SSH over DNS at the request of a client. It was pretty fun, worked surprisingly well. At the time, exactly zero firewalls stopped it.
ooh, MOSH over DNS. Theres all kinds of features to compensate for UDP lossiness built in.
Most tunnel protocols are UDP these days, vxlan, geneve, wireguard etc... Just because it doesn't guarantee delivery, meaning you don't get the retransmit amplification you'd get with TCP over TCP.