I'd be really curious on how hard programmatic access to your own, personal banking data might be in the PSD2-era.

I can link my secondary bank account to my main bank's app so I can see the balance in one place, but the catch is that I need to refresh this authorization through the app every 90 days.

Ideally, you'd just use your banking credentials to authorise the API access and pull data through that. What this requires in practice, I have no idea but it probably involves a bit of bureucracy.