I tried it, Dolphine also can't play the videos, on the phone the videos are running but when i use the dex brwosers there is a problèmes and i tried to use Mozilla and the athrs browser on samsung dex they have the same problems
Unfortunately (no it's a good thing actually) Adobe Flash is getting deprecated. It is insecure and inefficient. Modern websites and web browsers have dropped support for Flash since years. Linux is Flash-free since 2011.
The websites you attempt to visit must update their content ASAP