The groups in Al Tanf market themselves as Free Syrian Army (the original revolitionaries) and nowadays sometimes as Syrian Free Army.

https://syrianobserver.com/foreign-actors/free-syrian-army-in-tanf-changes-its-leaders.html

As said above, imo the groups in Al Tanf are simple mercenaries and have nothing to do with the original FSA.

But one thing they surely are not, they are not HTS affiliated.