So I'm currently in the endscreen. I want to add screenshots and a YouTube video as proof. Can I add the links to the endscreen report text or do I need to fill a ticket on the support site and add the links there?
Report for what?
The in game report is mandatory, then depending on the offense, you can send any additional evidence (screenshots/videos) with the players profile link to the support under https://support.deadbydaylight.com/ .
Survivors bodyblocking me in a corner and sandbagging, basically teaming with the killer
As said, report in game and open a ticket.
Also when you have doubts, you can always check this thread: https://forum.deadbydaylight.com/en/discussion/19450/game-rules-and-report-system#latest