Which current graphics card for cuda support?

Which graphics card is the best for a server?

And second question: Which is the best for a laptop?

It is off topics.
Here it’s an opencv forum.
Have you got a problem with cuda support in opencv?

Sorry, is that because the routines for NVidia?

I thought CUDA was the same as NVidia. Sorry, I misinterpreted it.

Is there a forum for my exact question?

You didn’t specify that you wanted to use it for processing with OpenCV CUDA. That said your question is too general anyway. The best graphics card for a server would be the best one Nvidia have on offer which is off topic.

What do you want to do, if its inference, check out the benchmarks for the models you will be using, if its image processing maybe extrapolating based on this performace comparisson I ran years ago may help