Reddit mentions of Anti Snore Devices Nose Vents - Snoring Solution for Comfortable Good Sleep and Ease Breathing

I've had very similar issues for almost 15 years now so here's my best advice for you to discuss with your doctor(s):

Nasal/Sinus Surgery is your last resort, it may very well be necessary but unless there is a structural anatomical obstruction you want to try treating the symptoms & seeing if allergies are the root cause before you go cutting stuff away which will help but is definitely not without side effects so scheduling testing at an allergist should be your first move.

In the meanwhile there are some things that can help open your nose up at night that are cheap & easy try out:
-wearing a Breathe Rite strip to bed is 1 cheap way to see if you can improve your breathing. If it helps at all there are reusable "nose vents" or clips to help breathing & snoring that are also cheap to try. I’ve found these most comfortable but YMMV based on what fits your nose best: https://smile.amazon.com/Anti-Snore-Devices-Nose-Vents/dp/B07MJ75MMW/
-Nasal Irrigation with a Neti Pot may help as well. NeilMed has a nice squeeze bottle starter kit. I like to exercise to open things up then do my nasal irrigation while things are opened up then shower
-If dryness is an issue at all I have found that rubbing Ayr Saline Gel inside my nose significantly improves my quality of sleep. Both antihistmines & Afrin can dry you out so that may help more than you realize

AS for Afrin the rebound congestion MAY be less of an issue if you're on a steroid spray so obviously try to not abuse Afrin but if it was me I would keep using Flonase or Flonase Sensimist until the allergist gets you on their recommended mix of meds. FWIW I’ve found NeilMed SinuFrin Plus better than my old fav Afrin Severe as it includes some moisturizing aloe & nasal dryness is an issue for me.

As always, ask your doctor about all of this & good luck feeling better! I know the misery all too well as you can probably guess