TL;DR
- Efforts like Graphene OS face increasing pressure from apps that refuse to run on non-standard Android.
- The custom ROM project characterizes Google’s approach to device attestation as incomplete and flawed.
- Graphene OS is prepared to take legal action if Google won’t let it pass Play Integrity checks.
You can put a SIM card in some older thinkpad laptops with that upgrade option. There are services like JMP that give you a number and let you use your computer as a VOIP phone. I haven’t tried JMP but it always seemed cool and I respect that the software is open source.
Skype also has a similar VOIP phone line service. Its not open source like JMP and is part of Microsoft. But in this context thats also a good thing, skype is mature software with enough financial backing to have real tech support and a dev team to patch bugs, in theory. So probably less headaches getting it running right which is important if you want to seriously treat as a phone line.