The LE11 Generic image now uses GBM/V4L2 graphics so there are differences to LE10. If you switch to the Generic-Legacy image it should replicate the LE10 experience, but no support for HDR (same as LE10).
The newer graphics pipeline doesn't support multiple outputs so the future update (when the Legacy image is dropped) would be to use an HDMI audio splitter on the (single) connection to the TV and feed the AVR that way (cheaper than replacing the AVR).
I'm aware of that effort and have spoken with the authors. To simplify the codebase needed for it to work on RK hardware they removed all the Amlogic support code so it remains a dead-end. And even on RK hardware the results aren't great (so they've said).
So what I would like to know now: Does shutdown work with LE 10?
There are no released LE10 images, so nobody knows.
It's not a debug log .. and you don't demonstrate the problem by playing anything. So not much use for investigations.
Unrelated to the problem, I do see that the Hyperion add-on is continuously faulting in the background. It's not supported under LE10/LE11 so you might as well disable / remove it.
Clean boot with debug logging enabled .. demonstrate the problem .. run "pastekodi" and share the URL so we can look for things.
Kodi feature requests should be made to the Kodi developers via the Kodi forums (when back online).
It works here 
Do we have to guess what kind of hardware you have?
Please post a full debug log. Primarily because it contains other information of relevance, but also because repeated failure to provide one when asked just means all the forum staff think you're a pirate trying to hide dirty habits and we ignore the thread.
Also ensure you are using the HDMI port nearest the power connector.
Question: Why do you expect Linux 4.4 vendor-kernel device tree content to work on upstream?
Question: How is this relevant to LibreELEC?
Use doubling and 1080 @ 60/59.94/50/24/23.976 modes (GUI may show 23.976 as 23.98)
Is the 25Hz material interlaced? If yes, you need to configure "refresh rate doubling" and 1080@60/59.94/50 modes and ensure 25/29.97/30Hz modes are NOT enabled.
Knowing how long this would take over my 100MB LAN..
^ Netgear 8-port Gigabit switches are £20 on Amazon. Switch from USB drives and Sneakernet to Ethernet and an SFTP client app (Windows to HTPC) that queues files and transfers them in the background while you're doing something more interesting.
LE is simply packaging Kodi into a distro. How Kodi handles add-on upgrades (for good or bad) is entirely a Kodi thing.
Kodi Settings > System > Display > Whitelist
Select 3840@30/25/24 and 1080@60/59.94/50/24/23.976 and enable "Allow double refresh rates" and leave the GUI resolution at 1080@60
It's a known issue. I rather lack the code knowledge to investigate and there's basically nobody else who cares for older Amlogic hardware around here so I wouldn't want to raise hopes of it being resolved 
When it fails you're dumped to the initramfs console. This is rather limited in capabilities, but you should be able to connect a USB keyboard and attempt manual mount of the BTRFS volume. I'd expect this to fail, but it might output some useful error messages?
