I'm on Graphene too and I once read that the modems used in Pixel phones are pretty trashy and drain a ton of battery. If I filter my battery usage by system, it shows that network standby almost consumes half of my battery charge (~46%).
Maybe the other guy here is right and it's a VPN issue (too)? idk. Anyway, I didn't really found a solution for this except leaving my phone on airplane mode at night.
Yeah I do have a similar fear. Valve is something special. I tried to hate them, they're filthy-rich corpos after all, but I can't. Something of value will be lost when Valve finally succumbs to enshittification, which cannot be said of a lot of other big companies.
But my fear isn't necessarily about Steam. I have like 20-30 games in my library. Steam is simply the least shit way to play games you have/want to pay for.