Is their any way to bridge a digital gap?

Hello Everyone, I wanted to ask if anyone knew any way to bridge a digital gap. The concept is similar to an air gap in infosec where the device is physically separate from the outside, only this time with emails and usernames instead of physically separate devices. This stems from self reflecting on my own digital footprint where many of my accounts are 'gapped' by having separate emails and usernames. Am I missing something? I am sure you could try using phone numbers to try and draw a correlation between the two, but is there any other ways you guys know of?