According to a comment on r/Wireguard, this error is caused by having the wrong kernel headers:
dkms packages (wireguard-dkms this time) need kernel headers for
current kernel you have loaded (uname -a). As long as kernel is
updated through apt or aptitude you should not run into problems, but
if you update kernel with rpi-update you'll likely get newer ...
I haven't followed the tutorial you used but wireguard is heavy under development and there are some outdated installation tutorials on the web. Try this Wireguard installation that uses an official backport from Debian Bullseye. I have just tested it again with success.
It should not make a difference if you run the root filesystem from a primary partition or from a logical volume. The operating system only sees the ext4 filesystem, no matter where it is located. Because you restore a complete backup of the SD Card to the logical volume there should also not be a difference.
The only thing I see is, that the display driver ...
... but I can't get any info on connecting from a pi
For this reason some times ago I have made a proof of concept but not completely finished it yet. There you will also find how to setup a Raspberry Pi as Wireguard client. This may give you some ideas what to do with your project. Have a look at How to bridge an access point with a remote network by ...
Installing the kernel headers
Your /etc/apt/sources.list.d/raspi.list is misconfigurated , you should have
deb http://archive.raspberrypi.org/debian/ buster main
(which provide the raspberrypi-kernel-headers package.)
instead of :
deb http://deb.debian.org/debian/ unstable main
(debian unstable repository, it will break your system if an apt-preferences ...
The question is very good explained with the diagram. But, sorry, it also shows that it is a very complex situation I can't give a detailed answer without access to the network to analyze its behavior step by step. And I'm afraid that it will be voted to close because it isn't restricted to Raspberry Pi. There are many other components involved for your ...
For those that have the same issue but had a working wireguard set-up, (Linux headers were installed in the past) a bad kernel update may provoke a Linux headers mismatch.
I tried the following command:
sudo dpkg-reconfigure raspberrypi-kernel-headers
and that solved my issue.