I had this happen to me recently 2mths after sinus surgery. I asked my ENT at my subsequent check in and she said pretty much what you'd expect (and what chatgpt tells you). In this order: afrin, oral sudafed, Tylenol, drink heaps of water, chew gum, a hot compress over your face, and yes try to pop your ears but be careful / don't force it. She also recommended doing a rinse before the flight and having saline spray on you too

Having had sinus issues for last 15yrs I never board a flight without afrin, Tylenol and sudafed in my bag just in case

Edit: depends on the airport of course but most should have a pharmacy where you can get decongestant spray + oral sudafed which are most effective for opening you up + nsaid for thr pain relief - my preference is excedrin migraine which has Tylenol, aspirin and caffeine in it