Despite sleep (the "wake up on every network event" kind of sleep) not being implemented in most PostMarketOS devices, I fucked around with my Redmi and found that the battery lasts much much longer on standby (if I don't forget to close the apps because they won't unload themselves)
If you have a whole ass Android container like Waydroid (instead of stuff like android-translation-layer being developed), you can just put MicroG there. Or whole ass Google services, if for some reason you decided it's a good idea. It's just Android.
But yeah, hardware support suckzzzz