Honestly AOSP (stock Android) isn't that different to Google's look, just more minimalistic and most roms will be based on AOSP with some minor tweaks. You could look into custom launchers, although not really an area I'm familiar with.
Agreed on notifications, I like to block the majority of them, which you can mostly do with modern Android versions. You might like to use F-Droid if you haven't already, since all apps are open source and not monetary focused, so tend to have less obnoxiousness to them as well.
Apparently the lemmy.world one is an "official" one built by the /r/pop_os mods, so probably makes sense to consolidate there. But yeah, it's all still shaking out in general and it probably won't be clear which is the main community/magazine initially for many places.