Macbook Pro M1 Max and 5K monitor

I want to connect my new MacBook Pro (16", 2021) M1 Max to my 5K monitor (LG 34WK95U).

All I get is lower resolutions 3440x1440, I have tried 8 different Thunderbolt cables of all types.

The only cable that gives me 5120x2160 is too short (0,4m), I think it comes from a Lacie HD.

Oddly this cable shows up in mac's system info as USB 3.1 (pic 1)

The others as Thunderbolt/USB 4.0 (pic 2)

I almost spent 150€ on cables I don't need and can't figure out how to solve this.

On a positive side I know they can work together at 5K, it's only a matter of finding the correct cable.

Anyone can help?

PIC 1

PIC 2