You might want to try installing kodi21 from RPiOS which supports wayland, and much like Xorg on the PC, allows the compositor (outside of Kodi's knowledge) to rotate the screen.
Note that this will use EGL for composition, rather than DRM which is a less efficient path. It should be fine for 1080p60, but will struggle with 4K video.
But you can give it a try quite easily, to see if it meets your requirements. Use the preferenced/screen configuration tool (from the desktop) to set the display rotation, then launch kodi (the desktop version, not the fullscreen version). You can switch the desktop kodi to use fullscreen when running.
To sum up; Popcornmix' solution with running kodi from rotated RPiOS (without LE then) is a verified working solution for this problem.