I am curious why you like about it. I was a Relay user, and it was the only one that was really good for me. I didn't care for sync, it seemed ok, but not quite good enough.
But after moving to Lemmy I went with Jerboa and Thunder. Both are good enough. What could sync possibly have that you pay for?
I know for relay I miss: auto mute. Everything is mute by default. Then slow and fastforward for all media, and a download button.
not OP, but the main selling point of Sync is an absolutely top notch buttery smooth and good-looking UI, adhering to Google's Material Design.
it looks and feels like a Google-made app, only it's made for nerds, so it's more configurable and maybe a bit bolder in terms of innovation.
in geneal this means: no loose ends, no jarring or lazy design, no janky transitions, and focus on ease of use (configurable gestures, bottom screen nav, presets, clever set-up tour, well thought out settings...).
of course you'll always find this one niche feature that someone Absolutely Needs which it doesn't have... and that's ok. can't have them all. but it covers 90 % of the bases and in terms of polish, you'd be hard pressed to find better. incl. Apollo, in my opinion (though it was some years ago that i used it).
I don’t understand the hate for charging for a product. I pay for a Mastodon client. If a Lemmy client that I really liked cost money and I felt the price was reasonable, I’d support that developer, too.