Planning to visit Edinburgh and fly back from London around 3rd week of May. Routes suggested on ua.com are hideously expensive ($8k in Polaris, via EWR for instance or $6k+ via TK with long transits in IST. Downside is far fewer PQPs).

Google flights shows a $5k flight (SFO-FRA-EDI, LHR-SFO), but the FRA-EDI flight in unavailable on ua.com (it is available to book separately as a one-way trip on Lufthansa).

Looks like my best option is to book SFO-FRA, LHR-SFO and get a separate ticket FRA-EDI (with the usual caveats re: impacts due to any delays).