Should still be available on Expedia. Depends on gateway cities. I bought MIA/IAD/LHR, open jaw CDG/IAD/MIA, 09/06-21, for $465 including all taxes and $5.00 Expedia booking fee. UA wanted $685 for the same flight. It is good fare (meaning, not error). Minutes after purchases, it is on United.com under my itinerary when you log in under your MP number.
The best value would be from SFO, PDX, SEA, LAX, to FRA, MUC, ZRH, AMS, via either ORD or IAD. Those are cities posted by people that are available. That is 1/2 the price normally one would pay traveling from West Coast to Europe in summer time.
The city pairs are all different, you just have to try by error, using multiple cities function on Expedia - roundtrip function will not pull up the S class fare.
East Coast cities include MIA, TPA, IAD - those are cities I looked at.
Could not find anything MIA/FRA, or MIA/ZRH that are this cheap, so I settled for LHR and return from CDG.
Good Luck.