Here's my current plan of attack, requires a reinstall of everything then a recompile of Asterisk (yeah, that bad):
Hardware: Raspberry Pi Zero W and ObiHai 110. Also have a 100 with Nat's firmware that I will try if this fails
Set your router to give your Pi and Obihai static IPs
Burn a Raspbian/Asterisk/FreePBX image to a micro SD (I used Etcher)
Raspbian - An OS for Raspberry Pi
Asterisk - a free PBX
FreePBX - a free web GUI for Asterisk
Boot it up
Login as root/raspberry
sudo raspi-config to change root password, set wireless settings and expand to the rest of the card (last under advanced)
sudo shutdown -r now
raspbx-upgrade
sudo shutdown -r now
raspbx-upgrade (again - sometimes this does more updates, sometimes not)
sudo shutdown -r now
Configure FreePBX by HTTPing from your PC to your Pi
Make a SIP Extension in FreePBX for your Obihai (don't worry about routes or trunks)
Change your Obihai settings to use it (SIP on port 5160 - NOT THE DEFAULT OF 5060!)
Keep doing this until your Obihai can log into Asterisk (you will see it on the SP1 Service Status on the Obi)
Do Module Update on FreePBX until they all are updated.
Make sure your Obi can still connect
Use Putty to connect from your PC to your Pi.
sudo apt-get install git
sudo apt-get install subversion
sudo apt-get install libbluetooth-dev
sudo apt-get install uuid-dev
sudo apt-get install libjansson-dev
sudo apt-get install openssl libxml2-dev libncurses5-dev sqlite3 libsqlite3-dev pkg-config
sudo apt update
sudo apt-get upgrade
Get the zip and follow these steps:
https://www.dslreports.com/forum/r32037680-PBX-GVSIP-for-FreePBXGet the three GV authorization strings you need (like refresh token) from
http://www.obifirmware.com/OAuth2/ Use FileZilla to sftp files back and forth.
chmod gvsip u+x
sudo ./gvsip
3 months later - when Google Voice changes who knows what yet again, scour the net for half written suggestions on how to fix the latest issue.
Suggestion #1 would be to try this all again. Who knows, it might work.
I've updated the list of steps several times today, keep getting further in the build script. If I do not post a success message, that means I gave up, more/different steps may be required or this may not be possible.
Update: Rebooted and fired up FreePBX. Can't connect to Asterisk. Asterisk logs show one error after another, LOL.