laibsch

The way I understand it is that you only need the full firmware package in a few exceptional circumstances.  What is the wifi chipset on your SBC?
 
Do you have the wireless-regdb package installed?  "dpkg -l wireless-regdb"

Thank you for reporting back.  I am happy to hear you were able to find another way to solve the underlying issue without needing the v4l2loopback-dkms package anymore.
 
I see you already have backports enabled but probably with low priority (as you should) by default.   You can check "man apt" for information how to install that specific version (or use aptitude like I do).  That being said, "sudo apt install v4l2loopback-dkms/bookworm-backports" should probably get you the version you need and hopefully it would install fine.

The OrangePi Zero 2w is maintained by the community and chraac in particular.  Maybe try to contact him by e-mail if you don't get a response here.  Or talk to other owners of the device here in the forum to see if they can answer your question.

/etc/apt/sources.list:1 and /etc/apt/sources.list.d/debian.sources:1
 
Those are the files and lines that are duplicate that apt tells you about

You should of course monitor the temperatures now to see if the board becomes abnormally hot (use your hand or the programs sensors or btop, for example).  That being said, a quick web search suggests to me that you are simply seeing a software problem AKA bug.  I suggest you open a bug ticket on the Armbian bug tracker and patiently wait for the board maintainer to have a look into the issue.
 
https://www.armbian.com/nanopi-neo-2/ lists https://github.com/spendist as the maintainer for your board.  Maybe you can send an e-mail?
 
sources:
https://forum.armbian.com/topic/9501-opzero-h5-after-update-41917-the-cpu-temperature-is-wrong/ https://community.nxp.com/t5/i-MX-Processors/IMX8MP-not-able-to-read-Thermal-zone0-temperature/m-p/1655665 https://community.nxp.com/t5/QorIQ/Temperature-is-not-available-at-sys-class-thermal-thermal-zoneX/m-p/1343009