TIL: #Tor added Control Port support for adding Client Auth in v3 onions, but only for the ‘client’ side (e.g TBB).
There is, as yet, no way to add the onion service side’s Client Auth settings via the Control Port.
In other words, Client Auth can’t be used with v3 *ephemeral* onions. (so not with #OnionShare, or even via Stem’s create_ephemeral_hidden_service())
https://lists.torproject.org/pipermail/tor-dev/2020-June/014375.html