I have an old Korean monitor with only a DVI-D dual link port. Compared to the crap-monitors at walmart, it still looks very good at 2560x1440. It can easily be adapted to Display Port using a "Club3D" brand adapter but there is nothing that will make it work with a laptop that only has HDMI: cheap passive adapters do not work.

So I thought maybe I could try a USB 3 dock with DisplayLink, maybe one made by Lenovo, with DVI and DP ports. (My laptop is old System76 with only HDMI, VGA, and no USB-C.) What is the current state of DisplayLink drivers on Linux? I have heard in the past that it is a laggy, cpu-hogging piece of crap. Is there a good USB3 dock anyone would recommend for Linux?

Anything that requires software rendering/acceleration instead of hardware is going to be a CPU hog. Let that be your guideline in deciding what to use.

Of course...but I was under the impression that DL drivers somehow or other could make use of gpu hardware.

I was hoping from some specific results from recent DisplayLink users so that I can decide what to buy. It sounds like things are improving somewhat:

https://www.displaylink.org/forum/sh...t=67355&page=2

but the final post does not mention which combination of dock and mobile gpu he is using.

I see several things about USB-C/DL ports on laptops and it seems that those as well as the docking stations with similar ports generally are well received. Do not have the references right now but they are available.

DisplayLink on Linux generally is horrible. They drivers only officially support Ubuntu, and even that's hit or miss, as the performance is truly abysmal if you try to do anything other than just display a desktop. Anything requiring 2d or 3d acceleration will cause system resources to be brought to it's knees, even on really good developer grade hardware (8+core, 45-watt TDP, 32GB ram).

Why not just get a HDMI to DVI cable? https://www.amazon.com/Amazon-Basics.../dp/B014I8UQJY

Also, a port that is USB-C may not have all the extras to enable video over it. But I have had good luck with a Display port to VGA adapter.