It might be a little useful for learning how to setup a receiver and dish aiming practice. Don't know if dish still has one open channel. Best I can remember is they used to leave the info channel (dish 101) in the clear.
You could use this to quickly find the very strong Dish transponder, learn how to peak a dish and double check the built in elevation scale on the fta dish you are working with. After finding the satellite you could mark the mast 110w or 119w. This will make finding a fta sat much easier - after swaping out the LNB for a fta unit.
As mentioned the circular LNB is in the wrong frequency range of 12.2 to 12.7GHz and you probably want 11.7 to 12.2GHz for FTA. Inside the DTV feed throat is a metal stepped septum, which delays one component of the signal to put it in phase with the other so the simple dipole in the LNB can pick it up as a linear pol signal. I doubt if you could get the septum out very clean unless you had a drill bit the OD of the feed throat ID to clean up the resulting mess. There are other types of circular pol feeds that use a plastic "dielectric card" in the feed throat for signal delay, which is usually easy to remove without any damage to the feed.
as far as I know there's only one bird that might be receivable in US/Canada that is in that frequency range an has linear polarization: ABS 3A @3W, as its Europe beam somehow reaches New England and the Maritimes (maybe also some of Québec?). And the sigmal is probably too weak for a DTV/DN-sized dish. I've never received it, and it's supposed to have a few Italian channels. Maybe someday i'll try