Hmm, I tested the vendor kernel on my Orange Pi 5 Plus, and it causes in infinite udev reload loop with persistent 5% CPU usage, due to one HDMI related device: Orange Pi 5 Plus | Network interface names can swap on reboot · Issue #6592 · MichaIng/DietPi · GitHub
While debugging our udev rule which assures fixed Ethernet interface names, the systemd journal was regularly written full and rotated due to the udev log spam.
Do you (anyone) as well see a udev worker process in your htop which never settles?