Hi,
this TV has the following features:
Board Type: TP.SK105S.PB802
Panel Info: T320XVN02.H

You have the last version, i think.

Some TV software uses an audio identification system based on the country selected in the installation menu, but if the audio codec is not associated with the country, it uses a different one. There are usually audio options in the menu, or there is an audio button on the remote control that allows you to change the language of the channel that is being displayed. You can also try a factory reset and test with a different country. I'm in Portugal and I've had similar problems with some TVs, it was necessary to choose a different country in the installation menu for it to assume all the audio codecs and work. They weren't TVs with this motherboard, but you can try doing this and you won't lose anything. It is also worth remembering that some more basic TV models are not compatible with more advanced codecs, especially high compression audio or video codecs, but this is especially the case with audio. I don't know if this is your case but I'm raising a possibility.

It's strange that you don't have other countries. It is certainly a version made just for Italy.
I am attaching a USB update for a TV with the same card but from another brand.
If you want to test it is at your own risk and you should be aware that it may not work or even cause the TV to stop working if it is not compatible. If you want to take a risk, proceed as follows:
Download the file and unzip it.
Place the files on a pen drive formatted in FAT32 format, you must place the files in the root of the disk (not inside a folder).
Connect the USB flash drive to the TV's USB port, turn off the TV, press the "power on" button on the TV and at the same time turn on the TV to the power supply. You should start the USB update boot.
But remember, I'm not responsible if something goes wrong.