> I thought maybe they run their own servers and thought it'd be worth trying
Unless the app you're using use the alternate push notification system e.g.Unified Push, There's no point in microG having their own servers. Demand your favorite app publisher to release a Non-GCM version of their app on F-Droid.
> I currently have GooglePlay disabled and I've never had issues with Signal notifications
Good for you, As I said its pull notification. In simple terms a scheduled local service asks the app's server whether you have new messages. The service needs to be active all the time consuming power, You'd probably seeing a pinned notification for it; Every pull notification app needs its own such service.
> I keep hearing this myth about how notifications can't work seemlessly without GCM. I don't believe it :)
Nothing to do with myth (or) belief system. Push (or) Pull is the technical fact w.r.t notifications.
Unless the app you're using use the alternate push notification system e.g.Unified Push, There's no point in microG having their own servers. Demand your favorite app publisher to release a Non-GCM version of their app on F-Droid.
> I currently have GooglePlay disabled and I've never had issues with Signal notifications
Good for you, As I said its pull notification. In simple terms a scheduled local service asks the app's server whether you have new messages. The service needs to be active all the time consuming power, You'd probably seeing a pinned notification for it; Every pull notification app needs its own such service.
> I keep hearing this myth about how notifications can't work seemlessly without GCM. I don't believe it :)
Nothing to do with myth (or) belief system. Push (or) Pull is the technical fact w.r.t notifications.
[1] https://unifiedpush.org/