A facebook employee explained me how tracking works. Its not the email address Meta is concerned about. Its the IP, device identifiers and location. Meta doesnt care about the email at all apart from sending you emails for notification. Even with a fake email they exactly know who you are. Let's say you visit CNN.com which has facebook tracker. Facebook has the IP and the device identifiers. Now you login with fake email account on Instagram, facebook knows that's the IP ans the same device hence it "must" be the same person That's how facebook creates shadow profiles.
That site says "Your browser has a unique fingerprint" even though I run Firefox, uBlock, Privacy Badger, and have privacy.resistFingerprinting set to true. My main problem may be plugins, once you have more than a few your set can be pretty unique.
It's almost impossible not to have a unique fingerprint online with how stuff is tracked. Websites are tracking user agents, screen resolution, your GPU/web graphics renderer, etc.
The only way is to disable JavaScript, but good luck to using the internet without it
Never heard about Tor Browser? Nice "privacy" community you've got here.
Iirc unique == identifiable necessarily, because your fingerprint might be different while still unique the next time around.