A big +1 here, avoid Google and embrace modernity.

I echo Igor Couto's comment. This feature would be fantastic and a great selling point for future customers, users and collaborators.

People are becoming increasingly aware of privacy issues, and how companies like Facebook and Google are using their private data to turn their users into products they can sell. A growing number of companies are leaving Google's "free" services in favour of more privacy-conscious offerings - including Proton (https://proton.me), Fastmail (https://www.fastmail.com), and Apple's iCloud. Upbase could help the trend by supporting services other than Google, too...

or to display tasks as a calendar you could subscribe to? I'd like to be able to see them at least, I'm not sure if this would be different/easier to Achieve?