naf at the DSLReports forum has modified Asterisk and it now supports the new GV-SIP protocol. This morning I got it installed on my RaspberryPi with the Raspbian OS. Inbound and outbound GV calls from my OBi110 work. The install includes building Asterisk from source. It's not as hard as it sounds. I also have it running on a PC with Ubuntu 18.04.
If you don't want to build Asterisk yourself, Nerd Vittles has a package:
http://nerdvittles.com/?p=26204
I have not tried this.
cant wait to try this out. Currently using Obi202 as proxies to multiple phones, an easy asterisk device would be much preferred. thanks for adventuring out!