- Distribute the releases publicly and notify users when a new version is available to download, but implement a more friction-less auto-updated mechanism for subscribers (this would require the user to "log in with patreon" in the app, which is not a problem since most of the app functionality relies on the user being online but could introduce some friction for individuals without a patreon account)
- Could distribute the source code only alongside build instructions, and have the compiled executables locked behind the subscriber wall, but I think it would greatly impact initial adoption
- Delay public releases of the application a couple weeks behind a "subscribers only" fast track which can get the latest version/release early (I've seen this approach used by a couple creators, such as the Cemu emulator)
- As I'll try to create a discord community around the product, can provide subscribers' discord accounts with privileges and access to exclusive channels for priority technical support and features request
From the user's perspective, subscription generally means web hosted service of some sort in today's software environment.
If this doesn't work for you, I'd look at an annual license. Bug fixes are made available all year but a new release with new features (with or without source code) is done every January. Older versions are no longer supported. Essentially, each new release comes with a new support contract.
This should be easy enough for most users to wrap their head around.