Tried recording osu for the first time but I noticed that it recorded with a black screen. Also tried recording with game capture but that seemed to not work either.
did you try to record with just display capture and without game capture and making sure all the settings are at the native resolution of your monitor or having the file save as mp4 because obs is working fine for me when I record osu
Make a new scene, a new display capture/ game capture, and have only osu! in it. If it still shows you a black-screen try switching to borderless mode instead of fullscreen.
If you still get a black screen and you have an NVIDIA Graphics card, then try the following steps:
Open the control panel.
Select "Manage 3D Settings"
Click on "Program Settings" tab.
Pull up OBS in the program list. If it's not there, add it to the list.
Open the application folder and select OBS64 or OBS32.