If I understand correctly, DP Alt Mode is chip or software-based and not cable dependent, so any USB-C cable will do.  This article has a basic introduction which I found helpful when looking at DP Alt Mode:  DisplayPort Arrives On USB Type-C | Tom's Hardware (tomshardware.com) 

Thanks, I have three USB-C cables and only one works, so I guess that's a gen-2 cable 👍

MikeAqua:

 

Thanks, I have three USB-C cables and only one works, so I guess that's a gen-2 cable 👍

 

all gen 2 cables I have seen are a lot thicker than gen 1, so that might help you when looking for gen 2

USB-C cables are a real rabbit hole. You can't always believe what it says on the box, and thicc doesn't necessarily mean it's better, but a lot of the time that's a good indicator. 

https://www.reddit.com/r/GooglePixel/wiki/officialguide/usbcinfo

wratterus:

 

USB-C cables are a real rabbit hole. You can't always believe what it says on the box, and thicc doesn't necessarily mean it's better, but a lot of the time that's a good indicator. 

 

https://www.reddit.com/r/GooglePixel/wiki/officialguide/usbcinfo

 

Yes, it's a bit of a nuisance when you need to purchase cable in a hurry.  In future I'll get the seller to give me something in writing that says what I buy, will support alt mode and power delivery. 

Yes nightmare finding ones that support the full spec.   I buy Thunderbolt cables instead as these have to meet minimum transfer speed and power specs and work with everything I've thrown at them (usb-c docks, daisy-chain DP monitors in particular).

USB-C chargers are an even bigger minefield than the cables. Right watts but wrong voltage means a no-go in many cases. And all the proprietary fast charging standards are all incompatible. Car ones are worse with them totaling up all the ports outputs to put on them even when it cant supply that with the fuse that is inside it.

I would say its a surprise that the USB consortium have messed it up so badly, but this is about the 5th time they have done something boneheaded and confusing that its just expected from them now. No enforcement of the trademark to maintain standards at all. At least HDMI are trying... poorly...