I think a better alternative would be a phone number.
You only give your number to friends, which aligns with the brand and product concept.
Allows more of your friends to join via your address book, good for the app growth.
Might also mean indirectly you can’t follow a non-personal page which also aligns to the brand and product concept.
Why people automatically think that social media should be like facebook and you should be global entity with billions of users? Wouldn’t actual social - in the literal meaning of the word - media mean that you share cool shit with maybe 3-10 of your closest friends who you actually see and hang out with, who are local to you? If you have an online game community, maybe you should meet once a year for IRL beer to tap phones? Perhaps we don’t live in a global village after all, perhaps we are are dumb tribal monkeys with super computers in our pockets?
* Tapping Phones * Confirming Phone Number * Confirming Email * Connected via Other Platforms (Facebook, Twitter, BlueSky, etc)
As far as maintaining a friendship by tapping phones, again, I would make the friendships a constant and graph / rank intimacy by how often you tap phones as well as how connected you are to your friend (phone, email, connections on other networks).
I'd make it so you could tap a phone, you know their phone number, you know their email. Importantly in my eyes, you shouldn't be able to navigate to a profile and just ask to connect as that'd mean you could do that to people you don't actually know (whereby knowing is inferred by you knowing some amount of their personal info such as tap, phone, email).
I'd stay away from your last option of 'other platforms', per my other reply below in that those platforms allow you to connect to anyone/anything. There is nothing in them that say this connection is inherently personal vs being generic.
The intimacy levels can be IRL (when you tap phones), Phone (when you friend via phone number) and Email (when you friend via email address). You could also measure the intimacy hierarchy / rank by keeping track of events (should events become a feature) you attend with other friends.
The problem I see with not using a phone number as I described, is that you'd be connecting to any old social profile - could be Messenger, WhatsApp, Instagram, LinkedIn, etc.
None of those are inherently personal, it'd open up Friendster to be not materially different to any other social network as those networks don't have the concept of a personal connection - they are just generic connections (some are personal, many/most are not).