The main issue during my earlier testing was that I was not applying the ClockworkPi kernel patches when testing older kernels.
Once I consistently applied the patches, I was able to compile and boot older kernels without issues.
Revised how-to (for reference):
# prepare environment (x86_64 running arch linux)
mkdir ~/tmp/uconsole
cd ~/tmp/uconsole
# source env.sh
source env_fish.sh
# env_fish.sh contains:
set -x ARCH arm64
set -x CROSS_COMPILE aarch64-linux-gnu-
set -x KERNEL kernel8
# get raspberry pi kernel sources and clockwork 6.12 kernel patch from rex's repo
git clone https://github.com/raspberrypi/linux.git
wget -O clockworkdrivers1.patch https://github.com/ak-rex/ClockworkPi-linux/commit/5633aedcb3fd632d64c54db0184880d1954de62b.patch
wget -O clockworkdrivers2.patch https://github.com/ak-rex/ClockworkPi-linux/commit/4b5b5fe35abbbf4193ddbeab149833172096066b.patch
cd linux
# pick 6.12.34 kernel
git checkout b2873db65
# apply the patches
git apply ../clockworkdrivers*.patch
# pick a different commit if the patches fail to apply
# cross-compile the kernel, modules and device tree blobs
make clean
make bcm2711_defconfig
make -j$(nproc) Image modules dtbs
# with sd card mounted in /run/media/jose/{rootfs,bootfs}
# copy the generated files
sudo make INSTALL_MOD_PATH=/run/media/jose/rootfs modules_install
sudo cp arch/arm64/boot/Image /run/media/jose/bootfs/kernel8.img
sudo cp arch/arm64/boot/dts/broadcom/*.dtb /run/media/jose/bootfs/
sudo cp -r arch/arm64/boot/dts/overlays/ /run/media/jose/bootfs
Also, I was able to bisect to the specific commit that introduced the issue and reported it at usb: dwc2: regression in split interrupt handling breaks FIDO (YubiKey) behind hub · Issue #7282 · raspberrypi/linux · GitHub.
@Rex Is there any chance you could build a separate .deb kernel package with 5329a41 reverted (until a proper solution is found)? Thanks.