For kicks, this image (LE13/master, so backup /storage/.kodi first so you can revert to LE12 after) is compiled with 4K pages:
https://chewitt.libreelec.tv/testing/LibreELEC-RPi5.aarch64-12.80.0.tar
Go experiment and see if that resolves anything?
EDIT: now linking the right image 
Time starts from the libc compile datetime (not last boot) and then jumps forward to current time when NTP kicks in.
Just "rpi-eeprom-config --edit" .. drop the -E
dmladenov I'm interested to see if the latest image: https://chewitt.libreelec.tv/testing/LibreE…h64-12.80.0.tar will handle VP9 media correctly. I added some patches to handle GXLX hardware so it should software decode (badly) instead of showing a blank screen or crashing or some other form of failing to hardware decode the content (as the silicon doesn't support VP9).
"sudo -E rpi-eeprom-config --edit" no work in Lebreelec
You are the root user so "sudo" is not required.
Thread renamed and moved to the Allwinner section. AFAIK we don't have support for H313 chipset yet, but I'll let others comment.
Argon cases have a bit of a reputation here, but forums inherently attract more people with problems than people without them, so I wouldn’t read too much into the comment.
The NAS device supports multiple users and access rights, so create a "kodi" user with read-only access to media and then relax and watch movies. In the rather unlikely event someone compromises your home network and obtains the insecure password; they can steal copies of your movies, but cannot do more. If that risk bothers you, disable Samba and SSH services and the insecure password cannot be accessed.
What can i do?
Type "run" at the boot prompt to run from USB instead of installing LE to the internal drive.
I've not seen a specific success report, but LE12 runs great on RPi5 and since RPi5 uses the identical HAT spec as all Pi boards, it's not something I would expect issues from.
The usual rememdy for CEC issues that make no sense is:
a) Unplug everything
b) Turn everything off
c) Go make tea/coffee .. something that takes 10 mins
d) Reconnect everything
e) Turn it all back on again
It too makes no sense, but has a surprising success rate 
Are you running the Plex server on the same machine?
Nope. Plex on a Synology NAS.
I've been using the dontpanickodi version for ages .. works great.
LE boots from two files: KERNEL (the kernel) and SYSTEM (userspace) .. the latter is expanded on boot to create a virtual (read-only) fileystem. If you look at the SD card directly you'll only see the two files (and some other RPi boot stuff). You can unsquash or mount the SYSTEM file, but it will be easiest to just boot the RPi5 normally and do things from inside LE, e.g. from a booted device you can do "cp -R /usr/share/kodi/addons/skin.estuary /storage/.kodi/addons/skin.custom" to clone skin files, then edit on /storage. Once you have cloned/renamed/selected the custom skin you can use kodi-send --action="ReloadSkin()" to live-test changes.
You only get to that file with root privileges. If you need top-level security, you have to learn a lot.
Unless you access /storage/.kodi/userdata through the default enabled \\LIBREELEC\Config samba share with known user/pass credential (libreelec/libreelec). You can change the Samba credential in the GUI. You can disable the Samba server in the GUI. You can disable SSH passwords (or SSH entirely) in the GUI. So the defaults are (intentionally) a little open, but if that concerns you it's simple to lock things down. That will likely inconvenience you though. Catch22.
e2label /dev/sda1 "LABEL"Use e2label to set disk labels and the drive should be auto-mounted to /var/media/LABEL instead of the default behaviour of mounting to a path that includes the current /dev/device which depends on USB probe order (which cannot be controlled).
The latest https://chewitt.libreelec.tv/testing/LibreE…h64-12.80.0.tar contains another attempt at getting HiFi-Shield devices working. There's one dtb for the original/plus versions, and one for the v2 card. The dtb files are obviously named and can be seen in /usr/share/bootloader/amlogic .. You need to "mount -o remount,rw /flash" first and copy the dtb to the card, then edit the /flash/extlinux/extlinux.conf file to use the different dtb name. I believe the S/PDIF output should work. I'm not sure if the RCA/Phono outputs will work. Let me know.
Read my first post again