DVI standard doesn't support audio officially. Some graphics cards support non-standard audio-over-DVI. Search for audio settings at your BIOS / EFI. It's basically no LE problem.
Chances are you won't find such audio settings. I suggest an USB audio interface. Those ASIO interfaces for musicians work fine. The ASIO driver is part of LE's Linux kernel. Other drivers need some research whether they work with Linux.
The last thing I would try on config.txt (post #6, #8 and #12) is to add hdmi_force_mode=1.
If that doesn't work, quit the config.txt approach, and put the working tvservice line (post #7) into /storage/.config/autostart.sh.
You can also test LE 10.0 Beta official or nightly, but I'm not familiar with the HDMI mode syntax of cmdline.txt.
You could also try DVI mode instead of HDMI, because you originally had hdmi_drive=1, which is DVI. DVI approach:
hdmi_force_hotplug=1
hdmi_ignore_edid=0xa5000080
hdmi_cvt=720 576 50 3 0 1 0
hdmi_group=2
hdmi_mode=87
hdmi_drive=1See edit above. I made a mistake.
Edit: New config.txt:
hdmi_force_hotplug=1
hdmi_ignore_edid=0xa5000080
hdmi_cvt=720 576 50 3 0 1 0
hdmi_group=1
hdmi_mode=108
hdmi_drive=2As mentioned, config.txt defines the HDMI mode on LE 9.2.7. Some of your settings are wrong there. Try this config.txt:
hdmi_force_hotplug=1
hdmi_ignore_edid=0xa5000080
hdmi_group=1
hdmi_mode=26
disable_overscan=1The problem is the interlaced mode on LE 10.0 Beta. Better use LE 9.2.7 for this. If you downgrade, backup / restore will not work. So do a fresh installation of LE 9.2.7 on microSD.
Please answer my questions precisely. Please open a new thread for this.
Because the black bar issue has been solved, I close this thread. One issue, one thread.
Do you use LE 10.0 Beta? If yes, then HDMI mode settings have been moved from config.txt to cmdline.txt.
Do you use an RPi4? If yes, use the HDMI port closest to the USB-Type-C connector (power supply).
Do you have no sound since converting your videos to black-bar-free? If yes, check the audio options of your converter tool.
Fine, stay tuned! 
Thanks!
Jul 05 18:40:00.805362 LibreELEC systemd[1]: Condition check resulted in Kodi user autostart script being skipped.Please post the content of your autostart.sh.
You're still at log level 0, so we are missing some info. Activate debug logging at GUI (HUD will appear), and do it again.
PS: Reboot before running pastekodi.
Da Flex are you still on LE 9.2.6 as I don't have any issues?
No, a higher nightly. Dev's currently update the add-on. There is a dependency among "colorzero" and "gpiozero", that has to be fixed.
I also have problems with RPi Tools. For me the GPIO pins don't hold their state uninterrupted. I'll ask the dev's to recompile that add-on.
Linux drivers are part of the Linux kernel, so chances are it works out-of-the box. If you want to go into details, get the name of the DAC and compare with the driver list of the current Linux kernel for RPi.
Do Beta-Auto-Updates on Raspberry 4 work at the moment or do I have to update manually from 9.95.3?
Read the release notes.
Yeah, stop screwing things up, and keep that working code! 
Seriously, it's more complicated than that. Read this thread for details: Click!
