On Buster a very different Kodi build, v18.7 from the Raspberry Pi repository is installed. That worked well for the last two years. The kernel is the same on Buster and Bullseye. It is Kodi 19 which seems to cause the issue 
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The issue with CEC is also known. A special build from RPi devs is required, but that exists for Buster only currently: https://github.com/MichaIng/DietPi/issues/4881
The issue provides a workaround for cec-utils, but I think it won’t work for Kodi as it was build against the newer libcec6 (the workaround installs libcec4 from RPi repo).