Well, even if you are not popular, you can have your site to show something or present yourselt and use it as your proof of identity. These days you can have a site for $10 /year.
Discussion
I already have a website .. 10 dollars an year I pay .. it is listed on my profile .. but anyone can put a site name there .. how do I link it to my profile such that it becomes my ID ? my side is https://shutri.com ... I post my npub.pro feed there ..
You can create a file /.well-known/nostr.json on your site and put your pubkey there:
{"names":{"_":"your_pubkey_hex"}}
Pubkey must be in hex, not 'npub' form - use nak.nostr.com to convert.
Then you put _@yoursite.com to your profile into NIP-05 field.