I have most of the clients installed and sync is one. Honestly never paid a cent, never saw an ad, never felt compelled to pay for anything.
I sympathize with those concerned about its data tracking, which is supposed to only be there for the limited ad revenue. But the dev asking for payments for features? It’s nonsense to get up in arms about that.
You should be able to make a living off of development skills as long as it’s done ethically.
Edit: hey I am an idiot. I forgot that I set my phone’s dns to an ad blocker one. Without it, perhaps I would hate sync, lol.