Unsure what this may be related to but for a few months now my Wifi on my S20 Ultra has been pretty bad when far from my Comcast/Xfinity (1-gig ) router. I used to have a pretty stable and strong signal upstairs - not far from router. Recently it very slow or just does not connect. Other devices on wifi upstairs work fine (tablet, laptop). Restarting the phone or router does not help. If i get close to router it seems better.
Unsure if related to Android 11 or other phone software updates but this just started in last few months.
1. Have you tried resetting network settings in Settings > General Management > Reset > Reset network settings
2. Try submitting an error report through the Samsung Members app!
3. What software version is your S20U on? (Settings > About Phone > Software Information > Build Number [last 4 characters])