Their objective is literally to know the least about you
Why can't mulvad tie account numbers to npubs. (They could) Please! nostr:nprofile1qqsdru78zcu6uwa6zlludjx7k87m8ft9q6e5jgsn6qe49rxzj9frwpqpz4mhxue69uhhyetvv9ujumt0wd68ytnsw43qdgkgx7
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And there is nothing inherent in having a nostr account that says anything about you.
Nostr is not aimed to be a private network but the hole purpose of mullvad is to maintain your privacy, whats the objective to linked both?