Media keys on my Corsair K70 do not work while Brave is open. It doesn’t have to be the active window to stop them from working. As soon as I close Brave, they operate as normal again. I have already toggled the flag for Brave to control media keys to no avail.
Windows 10. Brave Version 1.20.110 Chromium: 88.0.4324.192 (Official Build) (64-bit)