Allo Piano 2.1 DAC hat initialization failure with raspberrypi2-kernel4 6.6.28 and 6.6.31

[lightdot]

The Allo Piano 2.1 DAC hat fails to initialize using either:

raspberrypi2-kernel4-6.6.28-20240423.v8.1.el9.aarch64
raspberrypi2-kernel4-6.6.31-20240529.v8.1.el9.aarch64
raspberrypi2-kernel4-6.6.31-20240529.v8.2.el9.aarch64

From dmesg while running the latest:

[    6.271562] snd-allo-piano-dac-plus soc:sound: snd_soc_register_card() failed: -517

The last to work is raspberrypi2-kernel4-6.1.31-v8.2.el9.aarch64.

It seems vcdbg and dtoverlay aren't available... what else can I use to gather more information?

Relevant part of the /boot/config.txt:

## Allo Piano 2.1
##  disable onboard sound card
dtparam=audio=off
##  enable DAC
dtoverlay=allo-piano-dac-plus-pcm512x-audio

Using RPi 4 Model B, 4 GB, with AlmaLinux 9.4, fully updated:

[user@raspberry-pi ~]# egrep -w 'Revision|Model' /proc/cpuinfo
Revision        : c03114
Model           : Raspberry Pi 4 Model B Rev 1.4
[user@raspberry-pi ~]# cat /etc/almalinux-release 
AlmaLinux release 9.4 (Seafoam Ocelot)

_{For anyone that might find this useful, boot into an older kernel with the following added to /boot/config.txt (naturally, you need to have the raspberrypi2-kernel4-6.1.31-v8.2.el9.aarch64 installed):}

kernel=kernel-6.1.31-v8.2.el9.img
arm_64bit=1