Is it possible to have a TLM that fulfills the Sunday obligation on a Saturday evening?
It would certainly appear to, if you can find one so scheduled.
Can. 1248 §1. A person who assists at a Mass celebrated anywhere in a Catholic rite either on the feast day itself or in the evening of the preceding day satisfies the obligation of participating in the Mass.
It does fulfill the Sunday obligation, although I’ve always thought it’s unfortunate to have a TLM at a time that would have been foreign to the culture surrounding it.
The SSPX in Oak Park, Ill, offers a TLM at 6pm on Saturdays if you can believe that.