I have had this, too. I really feel for you. Someone on here posted that is related to acid reflux and not the sinus. He said a pulmonary specialist told him that it is laryngopharaengeal reflux.
When I read about it, it sounded apt.

Found this:

"In non-intubated patients with COVID-19 infection, vocal fatigue, dry throat, increased phlegm production, dysphonia, cough, rhinitis, and dysphagia have been reported as direct symptoms of the virus [18], [20], [21], [22]"