Windows 10 and audio over optical cable

Hi,

I recently purchased new speakers, Logitech Z906. I am trying to make the digital output of W10 work with my speakers (over an optical audio cable).

My specs:

motherboard MSI MPG X570 GAMING EDGE WIFI

speakers Logitech Z906

an optical cable Star II OPTO Tosslink<>Tosslink

current audio driver: Realtek UAD, v. 6.0.8858.1 (12/10/2019) – the driver provided by MSI on the support page for my MOBO

What I tried:

I downloaded a DST sound demo from here: Animated Logo (Lossless), audio: DTS-HD MA 5.1 48 kHz.

When played through VLC (and enabled DST in preferences), I can hear properly all 6 channels.

In the device properties (Realtek Digital Output Properties)>Supported formats tab>Encoded formats section I tested DST audio and Dolby digital and both worked on all channels.

The problem is no other audio except for these two tests gets played through the digital output.

My understanding of the problematic:

Optical cable connection is superior to the 3 x 3.5 mm jack connection because of a more quality sound immunity to magnetic fields (since there are quite a few cables behind my PC already with all those speakers, other peripheries, a lamp and so on).

My question:

Is there a way to get all audio (system sounds, browser, games, other applications...) to be played through digital output?

If not, am I correct the proper configuration of speaker connection then should be BOTH optical cable and 3 x 3.5 mm jack 6-channel audio? Then most sounds go through 3 x jack and only certain media (e.g. a movie with DST sound played with VLC) will be sent through the digital output?

I do not have the possibility of connecting the speakers through an HDMI port.

Thank you all for help! :)