> so many client/server implementations don't implement the datagram extension properly

I'm genuinely interested in what aspects you think are (or were) not implemented properly.

I wrote most of the implementation of quiche's datagram extension and, well, if there's something that can be improved, I'm all for it.

(aside: I think the standard should've considered an option for datagrams to opt-out of congestion control, given that most applications which want to take control over datagram sending probably also want to take control of available bandwidth and control congestion differently - e.g. by dropping encoding bitrate instead of queuing - but it is what it is).