If you enrolled in IDNotify (part of the Max or Premium Services package), that company might have notified you about suspicious activity. You need to log into your IDNotify account to check what they have on file for you.
https://ttlc.intuit.com/turbotax-support/en-us/help-article/account-management/sign-idnotify/L33FBuj...
In general, there is nothing alarming about your phone number being on the "dark web." Not too long ago, everyone's phone number was in a paper phone book and every phone customer had a copy, unless you paid extra for a private listing. The fact that your phone number is on the dark web just means that out of 10 billion possible US phone numbers, yours belongs to a live person. You might get a bit more spam phone calls than usual. You could contact your carrier to change it, but that carries a lot of hassles. You should be a lot more worried if your birthdate, bank account numbers, or credit card numbers were exposed.
