I tried to reproduce the issue a few days ago ,but i couldn't ,so i will try again asap.
Did exactly what you did,shutdown the TV and after 3h powered on again....no problem .
BTW ,my RPi4 is connected to a Soundbar which is connected to the TV via HDMI ARC.
CEC is also enabled .
Mine is straight to tv, CEC disabled, booting from USB-connected SSD. When on nightly from 25/9 and before i can have tv shut off for days without any problems when turned on again.
Updated to latest nightly, rebooted ok, turned off tv for 3 hrs, turned tv back on, No signal.
SSH "systemctl restart kodi" dosent help, only way to get it working is to pull the power and restart with the nightly from 25/9.
My Banana Pi M5 with latest CoreELEC nightly still works fine on same tv.
Switching sources doesnt help. All settings in CEC is set to Off, CEC is turned off.
Its no big deal, i have a working Shield Pro and a Banana Pi M5 with CoreELEC on the same TV, i just watch my movies through one of them instead.
I will stop trying to update LE until there is a EEPROM-update that solves this problem.
Back on 20221025 again today after trying LibreELEC-RPi4.arm-11.0-nightly-20221011-748a452, same problem; No signal when LG 65CX is turned back on. Only way to restart the Pi is pulling the power cord, reboot from SSH dont work.
My Pi reports Bootloader 2022-04-26 as being the latest.
Maybe nobody has their drive connected to the Pi directly and access over LAN or something.
I have one Pi 4 with several drives attached, but i dont run LE on it, i'm using https://www.openmediavault.org/ and share mediafiles from that to my other Pi's via smb and to my LG 65CX via DLNA.
In have stopped using 2 of my 3 Argon cases, only using the very first one i bought for my PI3B+.
No log means no problem
Probably not gonna start messin with that on movienight, and besides, it works perfectly fine if i stay on 20221025.
Last tested was LibreELEC-RPi4.arm-11.0-nightly-20221006-f15e1de, same behaviour.
After LibreELEC-RPi4.arm-11.0-nightly-20220925-b1d73ad whenever i turn my tv off for a couple of hours
or over night (i never shut my Pi 4 down, just reboot on ocasion when up or downgrading) and turn it back on it says No source, but all the leds on the Pi4 is flashing like normal.
If i downgrade to LibreELEC-RPi4.arm-11.0-nightly-20220925-b1d73ad everything is back to normal,
i can shut down my tv over night and turn it on again in the morning and start watching movies as usual.
My Pi 4 boots from USB-connected SSD.
LTS seems to be smaller in size and 1 USB3, not 4 like Pi3, same SOC and RAM.
Im using a Banana Pi M5 with CoreELEC 19.5-Matrix_rc2 (July 27th, 2022), works pretty good.
Chrome on Win 10 reported the URL as unsafe for hours today.
https://test.libreelec.tv/ is working.
Probably a Pi4.
Check if there might be others with that have the same problem: https://forum.kodi.tv/forumdisplay.php?fid=162
One of my Pi 4 4GB runs LibreELEC-RPi4.arm-11.0-nightly-20220607-9d4c846 now, no problems with sound through HDMI to LG 65CX.
