There is an existing issue/thread on here that talks about the Pi 3Aplus not having composite video past OSMC July 2021 I think, and it has an apparent solution for that being that the new graphics driver has the wrong GPU memory allocation set for the 3A plus specifically.
This issue still persists however on my 3B model. I used the suggested 2020 November build and it did work fine. OSMC insisted on updating and I decided to give it a go and see if it would be fine just updating but sure enough it broke composite output. No Kodi ui after the splash screen.
On the latest image, I made the suggested change to memory for the 3Bplus, and it didn’t solve the problem for my 3B. HDMI output works fine just like in the other thread.
I know I don’t have the logs either but I could get them if guided. What could potentially be done to fix it?