DisplayLink doesn't work for gaming
 

Many games do not work with DisplayLink at all.

A good example is Doom 3. When trying to launch it, nothing happens at all. Not even running it in a window helps. Game works just fine through other connections.

It's not really an adapter, it's more like a little GPU on a chip. So you're trying to play Doom on a crappy dongle GPU.

...of course it won't work. Plug straight into a real graphics card for that.

Example spec:
http://www.displaylink.com/integrated-chipsets/dl-3000

Hello,
That's not at all a GPU on a chip... That is an adapter.
The chip is a simple video decoder and does not do compute your graphics. That's what the link given explains.
The graphics desktop composition is done by the GPU in the machine. Windows gives it the job to do.

But, some games bypass the Windows desktop manager to improve performance and that's where we get the pixels from.
That should not be the case anymore in Windows 10, as the graphics architecture has changed.

Which OS are you using?

Kind regards,
Alban