Is the firm named "Keystone Collects.com" a legitimate tax collector for the City of Easton, Pennsylvania?

Here is their WikiPedia page: https://en.wikipedia.org/wiki/Keystone_Collections_Group

You might try calling the appropriate department for the city directly and inquire.

https://easton-pa.com/contact.html

Yes, that is a legitimate tax collections firm in the state of Pennsylvanis - https://www.keystonecollects.com/

TurboTax does not prepare (or e-file) any local tax returns in the state of Pennsylvania.  If you thought a city tax return was filed with  TT for you, it was not.