Since Game capture isn't working, I've found the following solution to work perfectly.
You don't have to run OBS in Administrator mode. It's the most simple solution called: Window Capture
Yes, I know I know. That also doesn't work flawlessly, but with a bit of change in the properties, it will work.
What is that hidden sauce, you might ask? It's called
Capture Method. By default, it's automatic. Simply change it to Windows 10 (1903 and up (
at the time of writing)) and you'll be able to capture valorant without issues. That's the solution I've worked with and it works like a charm.
TL;DR: Change the Capture method to Windows 10 and it will work.