A few years ago I considered buying out my TFS lease and on the phone w/ TFS rep, she indicated all loans would have to be originated by the dealer for TFS loans, which at that point instantly means a dealer will add some fees and other BS. The “only a dealer can originate a TFS loan” may be a state dependent thing however as mentioned its unlikely to be a competitive rate. The vehicle I inquired about initially was eventually sold to Carmax instead so that’s as far as I got in the process.
We do have this Wiki in LH that may be worth checking through:
The Best Finance Rates & Hacks! Submit your CU recommendations! - Wiki - Leasehackr Forum