GrapheneOS is a beautiful stop-gap, but there are real bona-fide Linux smartphones out there. To be clear, there are not many, the hardware often isn't great, the software often isn't great. PinePhone and Librem come to mind.
Cell carriers will just start requiring the attestation as well. And eventually, even an internet connection will - wifi routers will have to attest to ISP equipment, etc.
The final phase is "AI" monitoring everything you do on your devices. Eventually it won't just be passive, either, but likely active: able to change books you read and audio you listen to on-the-fly without your consent. It will be argued that this ok because the program is "objective".
At this point, I would stop using commercial cell carriers and ISP-provided equipment altogether, even if that means setting up mesh networks with an underground community. User control or bust.
I've been keeping an eye on FuriLabs (Furiphone). They maintain FuriOS - Debian with an Android kernel. Has a container for running Android apps. Price is reasonable though I don't know how it'll be affected by tariffs in the US. It's tempting.
Pretty sure Bunnie named it “precursor” because the plan is to make the actual phone (with a cellular modem) next. If I had the cash to support him and buy a Precursor I would.
Android is decades ahead of that in security, functionality, utility, devex, and design. It's a fools errand to try and modernize that, over building on top of AOSP.
