After One UI 3.0 update there are some problems
1) Ram management in 4GB ram version less than 800MB ram is available for user.
2) Battery drain is high.
3) Performance is low after update.
4) Sometimes device lags while scrolling.
5) No Carrier Aggregation even though requesting many times to Samsung even processor also supports it. So internet speed is low it reaches to about 70Mbps but in other devices it reaches above 100Mbps.
6) Poor WiFi strength
7) Camera autofocus is very slow to focus on object and for every shot it shows that "This shot might be blurry".
8. It shows a black screen while opening apps.
9) No Screen recorder in M21 but according to google android 11 should have screen recording option.
10) No Samsung Dex.
11) Charging speed is very less it requires 3hrs to fully charge even though it has 15W fast charging.
12) There is lot of heating of mobile and charger while charging.
