Trial+Payment Backend for Mac App & Chrome Extension?

We've got a small Mac App and related Chrome extension that we want to offer a free trial of and then charge a one-time fee for. We don't want to use Mac App store because doesn't work for Chrome Extension (would prefer one platform/system/workflow to handle either...).

Is there off the shelf software to help with this? Came across RevenueCat but not sure it does what we're looking for.

I know some people sell their Mac apps on Gumroad but doesn't allow for free trials?

Would love any ideas you all have :)