Curl script aborting, unrecognized audio device on Pi 4: mutiple issues when installing unipager on Raspbian bookworm

[ManoDaSilva]

I'm having multiple issues when trying to install Unipager on a fresh, updated/upgraded bookworm setup on a Pi 4.

First of all, the curl script seems to abort the install of the package

===> Installing UniPager...
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
The following additional packages will be installed:
  gcc-12-base:armhf libc6:armhf libgcc-s1:armhf libidn2-0:armhf
  libunistring2:armhf
Suggested packages:
  glibc-doc:armhf locales:armhf libnss-nis:armhf libnss-nisplus:armhf
The following NEW packages will be installed:
  gcc-12-base:armhf libc6:armhf libgcc-s1:armhf libidn2-0:armhf
  libunistring2:armhf unipager:armhf
0 upgraded, 6 newly installed, 0 to remove and 8 not upgraded.
Need to get 3,487 kB of archives.
After this operation, 13.7 MB of additional disk space will be used.
Do you want to continue? [Y/n] Abort.

===> UniPager installation completed.

After installing Unipager myself, the web server worked, but when specifying "Audio", no GPIO line is keyed, no audio out, and I get this error:
Detected Unknown Device
dmesg also reports a GPIO access error:
[ 852.577061] export_store: invalid GPIO 0

Seems GPIO access is at fault here, as the sysFS API was marked for deletion in 2020, and finally got removed in the latest bookworm release.

[ManoDaSilva]

Tried it on Bullseye and with a Rpi 3B+, same issue, "Invalid Unknown Device".

Can you please help? This is really an issue, and I can't really roll out more Dapnet transmitter without a fix somewhere.