$ gpg2 --keyserver hkps://hkps.sks-keyservers.net --search-keys 2071B08A33BD3F06
gpg: no keyserver known (use option --keyserver)
gpg: keyserver search failed: No keyserver available

WHAT?! I just specified --keyserver!!!??

Relax. You forgot the '.pool' in the url.

:facepalm: ... Apparently I need more coffee -- persistent failure state in user
encountered.

Sorry for the noise.

I do wonder about fault-tolerance, though, if a e.g. non-responsive host creeps
in to the pool.

At any rate, this is mainly a cosmetic issue at this point, and this bug report
probably contains sufficient information to help someone who "encounters" the
condition to resolve the protocol error quickly.