Just upgraded SBC/Duet 6HC now have error connecting.

[bug2k22]

I have just ran an upgrade on my pi5/6HC printer and am now getting the "Connecting....." and the error "Failed to open IO device: Error 2. Cannot open GPIO device file '/dev/gpiochip4'" when opening the wen interface.

I had forgotten I was still configured to update from the 'unstable/testing' channel so have probably picked up an issue not yet resolved for the next release.

Seems it has upgraded from 3.5.2 to 3.5.3-rc.1, the printer was working fine before the upgrade. How would I fix this issue?
Thanks.

[Edit]
I've tried downgrading the duet packages to the previous version with:

sudo apt-get install duetcontrolserver=3.5.2 reprapfirmware=3.5.2-1 duetsoftwareframework=3.5.2 duetwebserver=3.5.2 duetpluginservice=3.5.2 duetruntime=3.5.2 duettools=3.5.2 duetpimanagementplugin=3.5.2 duetwebcontrol=3.5.2

This completes, but with the error:

Setting up reprapfirmware (3.5.2-1) ...
[fatal] Failed to open IO device: Error 2. Can not open GPIO device file '/dev/gpiochip4'.

So I presume the Pi cannot communicate with the Duet board since upgrading the firmware of the board to 3.5.3-rc.1.

A look at /dev shows only the following gpiochip values:

gpiochip0
gpiochip10
gpiochip11
gpiochip12
gpiochip13

[bug2k22]

I found another article on setting up the DSF software and found that there is a reference to gpiochip4 in the file /opt/dsf/conf/config.json, editing the value of of following line resolved the issue:

"GpioChipDevice": "/dev/gpiochip4",

Changing this to /dev/gpiochip0 and restarting resolved the issue and I can now access the web interface.