Others have face the same problem and solved it by "feature unlocks", i.e. Working Copy (https://workingcopyapp.com/ https://workingcopyapp.com/), which sells 1

Others have face the same problem and solved it by "feature unlocks", i.e. Working Copy (https://workingcopyapp.com/ https://workingcopyapp.com/), which sells 1 year "pro" unlocks, and all features released during that year remains active even if you don't renew your pro unlock. It's not a subscription, as the software will continue to work just fine when the pro unlock expires, but you don't get new features. This of course puts pressure on the developer to keep coming up with new features, but then again that's the developers job.