[wrxtasy]

Simple question, which version of LibreELEC are you using, because this is the current advancedsettings.xml I package with my releases ?
ie. the largest possible to minimise 2160p video playback buffering.

Of course Zero Cache will not work as all cache data is written to the SD card which is hopelessly slow for write operations vs a SSD or HDD equipped Chromebox.

Code:

<?xml version="1.0" encoding="UTF-8"?>
<advancedsettings>
    <showexitbutton>false</showexitbutton>
    <cputempcommand>cputemp</cputempcommand>
    <gputempcommand>gputemp</gputempcommand>

  <samba>
    <clienttimeout>20</clienttimeout>
  </samba>

  <network>
    <buffermode>1</buffermode>
    <cachemembuffersize>157286400</cachemembuffersize>
    <readbufferfactor>20</readbufferfactor>
  </network>

  <pvr>
    <minvideocachelevel>10</minvideocachelevel>
    <minaudiocachelevel>15</minaudiocachelevel>
  </pvr>
</advancedsettings>

I do not recommend using Kodi Krypton at all on any AMLogic devices, there WILL be video sync problems there.

RSS Feeds are a known resource Hog, they should be ditched for ARM devices.
Android is also more of a resource hog than LibreELEC.
Comparing a Hub to an Intel i3 Chromebox (probably SSD equipped as well) is frankly pointless and actually pretty funny.
So a 2GB Skin into a 1GB device heh, are you mad ?

Sounds like you are trying to stuff an Elephant into a tiny Mini Minor car !
Gotta give you points for trying

I'm not seeing 23.976fps video sync problems either with WeTek Media player or LibreELEC Jarvis. No AVR in the HDMI chain tho.
Tested now with numerous 23.976fps test clips and scrolling movie credits.