I can speak on Cisco’s system or software, because I have always been suspicious of Cisco due to how massive they are, no company gets like that without dirty dealing underneath.
I don’t think Google forks Linux, they use parts of the kernel, and there’s also OpenBSD security code in Android as well.
While Google is evil and I will rejoice at the death of Google, I hope they are successful in their new OS to fully replace Android. I think it’s called Fusia. Software development is always better then GPL code is stripped out and replaced.
Buy an Android phone that you can flash to change the OS to remove all Google dependancies and use F-Droid to get all of your apps.