Subscription models only make sense for an app/service that have recurring costs. In the case of Lemmy apps, the instances are the ones with recurring hosting costs, not the apps.
If an app doesn’t have recurring hosting costs, it only makes sense to have one up front payment and then maybe in app purchases to pay for new features going forward
Personally, I don’t need yet another subscription service.
That being said, I’ve used Sync for years (Pro, so just ad removal, one time fee.), and just paid again for ad removal. I did this because I enjoy the app, and appreciate the effort that goes into creating and maintaining it.
I have no qualms about paying a person for quality work.
Tracking is for ads only, when ads are disabled then so is the tracking.
Which there is no way to verify as the app is closed source. So it’s just a speculation.