First of all, many many thanks for making Debian work on a Raspberry Pi 4B. I bounce back and forth between Bullseye and Bookworm on a Pi 4B and have noticed a performance degradation with Bookworm.
TL;DR
Install (current) Bookworm - performance good.
apt update/upgrade - performance tanks.
Revert 5.16 to 5.15 kernel - no improvement.
It seems that one of the 103 packages that get installed during the update causes this to happen.
Is there anything I can do to help track this down? (I hope the answer is not "install the packages one at a time to see what causes this.")
Thanks!