@james-milroy apologies again the delayed response, been a bit snowed under with work. At the weekend I finally found time to have a play and document it this time.

I thought I would try and start again, and document the process, and rather maddeningly sound worked with less fiddling. Here is the process I went through, my setup:

Picade 10”, using the USB-C Picade X HAT on a Raspberry Pi 4B 4GB

standard setup where a simple speaker in the Picade case is connected to the Picade X HAT via the 2-wire speaker connector on that HAT

In case it matters I have the USB power for the screen in the top USB 3 port

I also have all my ROMs on a USB stick in the bottom USB 3 port – which made starting from scratch a lot easier.

Using Raspberry Pi Imager I installed RetroPie 4.8 (RPI 4/400) image on a 32GB micro-SD card.
The Picade booted up this clean image fine, and the 10" display worked straight away (no commenting out HDMI lines in config.txt required).
After the initial storage resize reboot, it was at the Emulation Station configure input screen.
Using a USB keyboard, F4 to drop to the command line and run the Pimoroni Picade X HAT install script:
curl https://get.pimoroni.com/picadehat | bash
Then sudo reboot
This then finished in Emulation Station showing a black screen when the reboot finished.
Blindly press F4 again to drop to the command line and re-comment out the hdmi_force_hotplug=1 line in config.txt, then reboot again.
This time the Emulation Station screen showed correctly after the reboot – something must have changed as my Picade used to need that HDMI hotplug line enabled.
Sound is not working at this point, but feel free to configure the joystick and buttons now in Emulation Station.
If you were to run alsamixer from the command prompt you would see the familiar error about the hifiberry_dac soundcard not having a mixer, and no volume control being available.
Instead, just start an emulator from Emulation Station by selecting a game.
Sound now starts, at a painful 100% level.
Drop back to Emulation Station.
Open the menu and set the sound settings to:

Volume: 40% or your preference Audio Card: Default Audio Device: PCM OMX Player Audio Device: ALSA

Audio now works, and the volume persists over reboots etc. Dropping to command prompt and alsamixer shows a PCM volume control. Basically it’s working, and I can’t work out why it wasn’t working previously and why I had to fiddle with .asoundrc etc.

Again, in case it matters, the bootloader and eeprom on my Pi is up-to-date for default branch:

CURRENT: Tue 25 Jan 14:30:41 UTC 2022 (1643121041) LATEST: Tue 25 Jan 14:30:41 UTC 2022 (1643121041) RELEASE: default (/lib/firmware/raspberrypi/bootloader/default) Use raspi-config to change the release. VL805_FW: Dedicated VL805 EEPROM VL805: up to date CURRENT: 000138a1 LATEST: 000138a1

Finally, with sound now working I brought everything up to date, and sound still works fine:
sudo apt-get update && sudo apt-get upgrade -y && sudo apt-get autoremove && sudo apt-get autoclean

I do hope this helps, and works for others. Very best of luck! I'll keep my fingers crossed that mine stays working as it is now!

Picade Hat Breaking Emulationstation??