how do I create an image of the SD card that can be useful for later use with multitool on the TV box?
Sorry.. no idea and subzero interest in investigating the topic further. As a rule backup/restore of /storage contents is always easier and faster than trying to "full-image" devices so I'd recommend learning some basic tar/untar commands.
Banned add-ons are installed. Your problem is not our problem.
OpenVPN works fine here so it's something related to your configuration or a third-party add-on that needs updating not the OS image.
I really hope there's a way to get the wifi working
Not happening. The SSV6501P chip has no driver that works on Amlogic hardware and upstream kernels. Some Armbian devs have wrangled the rather horrific vendor code to use on Rockchip boards, but in the process of simplifying the code for their Rockchip needs they removed support for the Amlogic chip implementation. You'll need to use an external USB dongle for WiFi.
Put Kodi in debug mode and reboot, then share the URL generated by "pastekodi"
No log(s) provided.
Please provide/share some media samples that Pi devs can have a look at.
If the upstream kernel only shows normal 720p; that's what's supported. The better option would be using the HDMI input no the TV and having normal 1080p available.
Enable persistent logging in LE settings. Enable debug logging in Kodi. Reboot to generate clean logs. Then connect a USB drive and copy logs from the following locations to the USB drive using the Kodi file manager:
/storage/.cache/log/journal/*
/storage/.kodi/temp/kodi.log
Use the LE12 image as the LE11 codebase is now EOL and will not receive fixes (only add-on bumps).
Would you mind adding a ffmpeg plugin with the 4.4.x ffmpeg version as a alternative?
There's no info on your hardware/codecs/configuaration or Tvheadend configuration, and no debug logs .. 
So assuming there is a real problem (not related to client-side drivers) the issue should be reported to Tvheadend devs so it can be investigated. If the problem is in Tvheadend (as you suggest) that's where a fix is required; we have no interest in packaging retro ffmpeg versions for workarounds.
connmanctl
agent on
scan wifi
services
connect <service>Use connmanctl to join a WiFi network ^
<advancedsettings version="1.0">
<!-- enable debug logging -->
<loglevel hide="false">1</loglevel>
</advancedsettings>Then create /storage/.kodi/userdata/advancedsettings.xml with ^ that content and reboot so Kodi is in debug mode. Then run "pastekodi" and share the URL generated so I can see the system log and Kodi log.
Not sure how you are running Transmission (nor do we care to know) .. but it wasn't provided by LE so it's not something you will receive support on in this forum. Go read forum rules again.
Just checkout and build master as the start point. For what we're doing there's no need to commit/save changes.
Ubuntu minimial with openssh is all that's required; then you can SSH into the VM to install prerequisites and clone sources. There's no need for the GUI environment too, but I guess for some users Terminal access will be easier than SSH.
dhomas Have you tried a clean install vs. upgrade? (or stop Kodi and rename /storage/.kodi to sidestep all current config). I ran a boot test on LE12 to look at alleged audio issues with an ageing Xtreamer Ultra2 (ION) board a couple of weeks ago (first boot in nearly a decade) and audio was working for me.
However, I encounter an issue where Wi-Fi networks are detected but when I try to enter my password, it gives an error of invalid password, preventing me from connecting.
This is a general issue and nothing to do with your hardware or presence of Armbian. It is proving challenging to resolve as none of the staff can replicate the issue. See: https://github.com/LibreELEC/Libr…ment-2001716879 for the latest ideas on things to fiddle with.
You need to describe the configuration in more detail. It is not clear what you are trying to engineer/do.