Does anyone actually use HTTP_1_1_REQUIRED or HTTP_VERSION_FALLBACK?

Hi all,

HTTP/2 defines the error code HTTP_1_1_REQUIRED with the description "The
endpoint requires that HTTP/1.1 be used instead of HTTP/2.". The only
mention of this error code is in Section 9.2.1 that describes TLS 1.2 and
HTTP/2 and says

> This effectively prevents the use of renegotiation in response to a
request for a specific protected resource. A future specification might
provide a way to support this use case. Alternatively, a server might use
an error (Section 5.4) of type HTTP_1_1_REQUIRED to request that the client
use a protocol that supports renegotiation.

I was curious if anyone uses it this way. With the advent of TLS 1.3, I
presume an HTTP client wouldn't address this specific problem of
renogitation problem, so a client might need to do more complex logic. Or
it doesn't because nobody actually handles the situation as the RFC
describes it might happen.

HTTP/3 defines the error HTTP_VERION_FALLBACK with the description "The
requested operation cannot be served over HTTP/3. The peer should retry
over HTTP/1.1.". There is no example of how this error code might be used.

I thought I'd ask here to crowdsource some answers about whether these
codes are actually used in practice.

In some circumstances, when dealing with a semantic or application error,
resetting a stream with an error code instead of serving an HTTP response
with an error status can be problematic. The circumstances under which
HTTP_1_1_REQUIRED or HTTP_VERSION_FALLBACK could feasibly happen seem
rather niche and might actually be alright. I'm trying to get a sense of
that.

Cheers
Lucas