Two options:
a) Configure a static IPv4 address in LE settings add-on (network) settings
b) Configure the router with a static DHCP reservation for the MAC of each RPi device
I would personally do 'B' because this means the DHCP assigned IP is persistent over reinstallations of the device and copy/pasting things to a router GUI is usually quicker than entering details with a remote control (nothing has a keyboard attached in my setup).
See https://kodi.wiki/view/Adding_video_sources .. use SMB or NFS sharing from OpenMediaVault and it should be simple.
Connect the RPi4 directly to the TV (no AVR) and check the EDID data is readable. If it is, capture the EDID from the TV to file so it can be forced to workaround the issue the AVR is introducing. If it is not (and do this anyway..) try different HDMI cables.
The issue is probably the TLS cert chain in the image, which is now outdated so HTTPS connections fail when accessing repos.
See RE: Cannot Install/Update Addons
LE11 development image: https://chewitt.libreelec.tv/testing/LibreE…lepotato.img.gz
Kodi always and only outputs progressive. Interlaced 25/29.97/30 media requires 50/59.94/60Hz modes from the TV so that each interlaced frame (two half frames) can be rendered progressively (in two progressive frames). Hence the highest resolution Kodi can output is 720p (mode 4) and there is no 1080i to select.
What version of MariaDB? .. it needs to be something recent.
PR to bump add-on revs (followed by rebuild and push to repo) has been submitted so changes will come though. Be patient.
We generally try to avoid those kinds of scenarios but we're human and occasionally things happen. Life on the bleeding edge of development often involves some blооd being spilled 
"Long ago" probably means using the legacy video pipeline which means the hdmi_ tweaks in config.txt aren't relevant to the now-different video pipeline used in current LE releases.
LE 9.0.2 image is here: https://releases.libreelec.tv/LibreELEC-LePo…rm-9.0.2.img.gz
Once that's installed you can probably update to dtech release of LE 9.2.8 (search the forum for his release thread).
LE11 dev image with Kodi 20 and Linux 5.19 is here: https://chewitt.libreelec.tv/testing/LibreE…lepotato.img.gz
IIRC /storage/.kodi/userdata/favourites.xml ?? .. I don't think it's a DB file
Most monitoring tools have install scripts that assume sudo is needed and wrong path locations for LE, but as dependencies aren't complex the scripts can be adapted to run on LE without much effort. You can run more complicated things in Docker containers; but that's more for application stacks than simple things.
If you can point to an online location for the installer script someone can see what might be needed.
Just exclude the -w filename.pcap .. then it outputs to console
git clone https://github.com/LibreELEC/LibreELEC.tv.git
cd LibreELEC.tv
git checkout libreelec-10.0
PROJECT=RPi DEVICE=RPi2 ARCH=arm make image^ If you don't change to the libreelec-10.0 branch you are building against master and the driver will need patches for Linux 5.19.y
https://chewitt.libreelec.tv/testing/88x2bu.ko <= module built against 5.10.110 kernel (current HEAD of libreelec-10 branch)
http://sprunge.us/LDOzia works for me (no PKG_DEPENDS_TARGET required).
tcpdump -G 300 -W 1 -w dumpfile.pcap -nnpi wlan0 arp^ tcpdump's -G and -W options can be combined to do the same thing; meaning rotate the capture file after 300 seconds, write 1 file
It's impossible to advise without seeing the package.mk content