In a cave with a box of scraps

Have you checked the "Get Sync Ultra" and "Remove ads" items on the drawer menu (swipe from the left side of the screen)?

And if you don't buy any of those, then ads.

That's how.

They come out of the efforts of a single dev.

It comes from raw fuckin talent.

There are plenty of great apps developed by one or only a few people. I'm personally not surprised.

You get a good feel as to what the developer is like on his discord.

https://discord.gg/EdfD7UsB

Using Java and Kotlin.

I asked lj on discord after joining the dedicated server.

And yes he's paid through a combination of ads and the no ads / Sync Ultra purchases.