Originally Posted by
Skipcool3
Hindsight but could this work if you had booked LHR-DOH. DOH - FRA (-LHR) ?
Unlikely given DOH was still the turnaround point on the itinerary (be that to LHR on the return or even to FRA as per your suggestion) and not a transit stop as such. Destination as far as the flight itinerary goes is DOH at which point the return journey commences. This is where the passenger would fail entry requirements under current entry requirements - even if they say they intended to stay airside. With the airline fined for potential denied immigration, no airline will take that chance, even if the passenger guaranteed to pay it themselves.
Must have been a very important meeting for the OP to fly 6 hours in a mask and visor (QR requirements) just to have a relatively short business meeting and then fly home another 6 hours in another mask and visor.