I'm told by a VoIP expert who knows a lot that zoom in particular rejects SIP callers who are not offering video.
So much for using my phone for audio in SIP HD from my Obi to go along with any video I might use on my laptop.
There is also another issue when calling out to SIP destinations through a SIP Service Provider's link for purposes of the Obi's configuration, that it exposes my username to the actual SIP destination, something which only makes sense and perhaps should only be disclosed to the SIP server that needs it for registration purposes. I don't know any way around this.
The original nomorobo project (not the subsequent company with a service by that name) got around this when calling out from an Obi110 to forward land line calls to a SIP destination, such as a joke line, by sending calls through a Yate server over to a tropo script that did intelligent things.