It's essentially an open source fork of maps.me by the original creators.
I've been using OSMAnd for years, but it always felt laggy and not that reliable. Searching was slow and so on. Many street or things it didn't instantly find.
In the Graphene App Store I jnust discovered Accrescent (another app store thing but only with like 10 apps - they're all gold though, god damn)
An in there I found organic maps. And this shit is google maps level responsive. If you're on the lookout for a google maps replacement - consider trying this.
Byeeee
I just started using it, and I would say it's even snappier then G Maps. I was pretty skeptical at first, and it does have a few things I miss, like public transport live updates, but I can use the app of the local provider for that and in my experience G Maps can be quute inaccurate anyway. No way I'm going back now. You need some space to preload the maps though.