Even as a non-developer, I found this well written article of great interest. It explained a few things about #UnifiedPush I wasn't aware of, and has given me better insight into how it functions.
It's clear now that there simply isn't any excuse for developers to use #FCM for notifications. I sincerely hope UnifiedPush will gain traction, not only amongst #FOSS developers, but the Android developer community at large.
It's perhaps worth noting that users of #Conversations (and its forks) already have a distributor included in their client, thus further lowering the bar of entry.