We have Nostr addresses here, which allows you to be easily identified and searched for as long as the client that you're using verifies the address displayed to be valid. For nostr:nprofile1qqsgydql3q4ka27d9wnlrmus4tvkrnc8ftc4h8h5fgyln54gl0a7dgsprpmhxue69uhhqun9d45h2mfwwpexjmtpdshxuet5qy28wumn8ghj7un9d3shjtnyv9kh2uewd9hszrthwden5te0dehhxtnvdakqc267ea, he's now using Primal as his Nostr address. So you'd look for a valid jack@primal.net for his address.

If you're a well known individual with a known company or website, you can setup your Nostr address for verification that way. Jack used to be jack@cash.app, but he's since changed as mentioned above.

You can use a service provider such as Primal or my nostrplebs.com or the dozen or so others. Not all providers are as reputable as the next. Some require payments, some do not. Some disappear.