Metal doesn't work with wireless charging. Plastic feels cheaper. Still, many companies are making plastic phones, and I'm sure some are making metal ones as well.
LinuxSBC
It still has issues, but it's much better than SMS, which is currently the only option for messaging between Android and iOS.
Heat difference is what you can get energy from, not heat itself. You need something cold to get energy from the heat.
Luckily, pretty much any modern x86 CPU works about as well as any other. I've had a Ryzen CPU for about three years and an Intel CPU before that, and I notice no differences (apart from obviously the faster CPU being faster).
Yes, and also RCS.
A .ovh domain is more like $3 a year. That's what I'm using.
I used Google Messages directly for a while, but then a Matrix bridge that uses Google Messages was released, so now I use that. If you want to try it, matrix-docker-ansible-deploy makes it really easy to self-host, but if you don't want to do that, something like Beeper can probably do it.
EMS doesn't support bridges unless you pay for the highest tier, but the list you linked is good.
Also rooting in the first place and installing "modules" that extend functionality.
Sorry, I meant "the only built-in option for messaging between Android and iOS." A lot of people don't want to install any third-party messaging apps.