I'm going straight to the point. I bought a used Galaxy S10e and I transfered all my stuff via SmartSwitch from my old Galaxy A8 (2018). The WiFi on A8 was working perfect with no problems what so ever. On the other hand the WiFi on S10e is working baad. The capped speed for 2.4Ghz networks is around 10 Mbps (Down) and on 5Ghz networks about 50 Mbps (Down) (I dont have enought upload speed to test if the upload is also capped). This happens on all networks no matter where I connect. I tried forgetting, reseting, and turning off every network setting -> Didn´t help. But when I tried wiping the cache the wifi started working perfect for about 10 minutes than it suddenly capped the speed again. I tried other devices and I´m getting full 2.4Ghz speed (around 50-60 Mbps down). The ISP is providing me with speeds around 100/10 Mbps.
The first picture is a 5Ghz test and the second one is a 2.4Ghz test.