I'm also a Go+SQlitemaxxer. For my first SaaS I focused on keeping the list of external services very short, as I basically couldn't afford it. I only picked those services that were a) vital b) could be replaced with a homegrowned/FOSS alternative.

Besides keeping the costs down, I find that this approach makes it way more enjoyable to build and easier to manage than having 10 services/subscriptions.

*PS: I think that you could add a small QR Code for the iOS/Apple installation on your app's website.