Been poking around a bit more, and found another entry in the Firewall that comes up right on boot, which is a service called MS.Edge.Webview2, which seems to be triggered through the Teams App (that I did have on autostart). I’ve now completely uninstalled Teams, and after a fresh boot the ad (or “media control”) seems to be gone now. Guess I’ll be using Teams from my phone or via browser in the future. No idea how that happened though, I never played any video through Teams.