Here in the US I managed to get an extra 6 feet for under 20 bucks with one caveat.
I used this for displayport and this for USB.
The caveat is that there's a very slight visual snow effect. I've been told it can be removed by putting a displayport repeater between the index and the extension, but I haven't been bothered to do it because I can only notice it when standing still in very dark environments, and even then it's really not that bad.
I say that as someone who was willing to spend $1000 to have great visual clarity in VR. I would say 95+% of the time I cannot notice it at all, 3% of the time I can notice it, and 2% of the time it's a little annoying.
These worked great for me.
Club3D CAC-1022 DisplayPort to... https://www.amazon.com/dp/B07RJ13CH9?ref=ppx_pop_mob_ap_share
Cable Matters USB to USB... https://www.amazon.com/dp/B00C7S2FRE?ref=ppx_pop_mob_ap_share
Which I notice you have tried. But I can confirm they should work.
Dunno if it will help, but I have an Odyssey + and this is what I use:
I used the DisplayPort cable you linked for a couple months without issue even at 144hz but eventually started getting sparkles regardless of refresh rate. My best guess is that kicking the breakaway cable loose a couple dozen times loosened the connector enough to degrade the connection to the point that it couldn't handle the extra length. Wound up just moving my PC closer to my play area and going without extensions.
That said, this is the USB cable I used and I had no issues using it though this USB card, but when using the USB ports on my motherboard the Index's cameras wouldn't work.
Cable Matters DisplayPort to... https://www.amazon.com/dp/B00L1K1G74?ref=ppx_pop_mob_ap_share
Cable Matters USB to USB... https://www.amazon.com/dp/B00C7S2FRE?ref=ppx_pop_mob_ap_share
These work for me.
I ended up with a powered usb hub (great for button box and other add ons as well as a 6 ft usb cable. Links below:
Powered USB Hub 3.0, atolla USB... https://www.amazon.com/dp/B07MQDJLSF?ref=ppx_pop_mob_ap_share
Cable Matters USB to USB... https://www.amazon.com/dp/B00C7S2FRE?ref=ppx_pop_mob_ap_share
I use an hdmi extension cable with this displayport adapter and a usb 3 extension cable with this powered usb 3.0 hub. It's worked out really good, the powered hub solved the audio static issue, I got the recommendation here, I think.