[octoberfranklin]

That is not as common as you think, and will get less common as QUIC grows in popularity.

If you're really really desperate you can send UDP packets with fake TCP headers (i.e. you aren't actually doing any congestion control or retransmission) but you have to control both ends of the connection for that.

And there's ICMP.

[bnjms]

Blocking UDP to Outside and non-ping udp to Outside is common. It will remain common as long as servers fall back. And exceptions will be made for problem domains.