On my personal non-business account I have created a Firebase project and set up the hosting which I am using to serve my app.
This is under domain name: Quantified-self.io
Now I would like to enable and receive emails for that domain via the Google Business (dimitrioskanellopoulos.com) account that I have for my company. I read on Google Business that I can add a secondary domain.
However, I am not sure if this will create a problem.
So if I add the domain that is used from my firebase project (quantified-self.io) to my Google Business account will things still work, or will this end up to some unexpected behavior/disaster of my firebase app?
I can answer this from the Firebase side at least -- Firebase Hosting is not aware of anything related to Google Business and will continue to work so long as your DNS A records are pointed at the correct IP addresses and your domain does not have CAA records preventing certificates from being created.
If adding the domain to Google Business just means adding some new TXT records for verification and/or setting e.g. MX records, you should be fine.