I totally understand your reluctance to have sinus surgery and my experience may give an idea or two.
Background: I’m new to bronchiectasis. It appeared on a followup CT in Jan. I’d had CT with many nodules/mucus plugs thought to be MAC Aug of 2022. . I was also diagnosed with asthma by the pulmonologist then. After second CT, I was sent to ENT and chose to go to Mayo for consult in March. MAC cultures ended up being negative.
I’ve also had long termsinus problems with a septoplasty years ago.
I requested allergy testing this spring and have severe pollen allergies. I also had opaque frontal sinus on CT.

A few things from my experience that may be relevant for you.
1. One theory is that the post nasal drainage caused the mucus/nodules in lungs and then bronchiectasis. Another is that I might have had MAC and cleared it.
2. Azelastine nasal spray really helped decrease my drainage and dramatically improved my horrid cough when combined with Flonase, which never helped alone. I thought Azelastine was a miracle drug. 🙂 Mayo changed it to a compounded “triple nasal spray” to add Atrovent to the antihistamine and steroid.
3. A short tapering dose of high dose prednisone with Augmentin helped nasal congestion a lot, but didn’t clear frontal sinus.
4. Tobrax eye drops that local ENT had me use in nose while in a head hanging position seemed to clear it. I did it for about 6-8 weeks while waiting to get into a frontal sinus specialist for possible surgery. When I finally got into specialist, frontal sinus had cleared.
5. LocalENT had also mentioned a procedure using ablation to decrease drainage, but University ENT didn’t mention it.
6. I still had a lot of post nasal drainage at frontal sinus specialist ENT appointment in May and he started me on Mometazone added to Neil Med saline rinse and encouraged sinus irrigation 2x/day.
I don’t know if any of these meds would help you, but it might be worth asking. Good luck!