Just like to share the issue that I am facing when using Samsung Dex on my S21 Ultra:
When using Samsung Dex, my S21Ultra will constantly screen wakes up by itself whenever I use my external keyboard to type on web browser app or and other apps that requires typing. I’m using an USB dongle for my external keyboard and mouse. I have tried testing the same setup on the following devices, S20Ultra, Note20Ultra and Note20 5G (All devices are on the latest software) and nor of them face the screen waking issue when typing. I have even go to an extend to factory reset my S21Ultra and it did not solve it. I strongly believe it is a software issue that needs Samsung Mobile Software Team to look into and fix it.
One UI version: 3.1
Android : 11
Android security patch level: 1 May 2021
I hope there will be a hotfix software update soon to remedy the problem ASAP as I am using Samsung Dex on my S21Ultra for my work. Do drop me a reply if if you manage to find a solution to the problem