[ubuntu] Put in first Dedicated/Discrete Video Card, with 'buntu OS's installed or not?

Often it works directly to add a graphics card. The built-in drivers can manage it. There are exceptions, particularly with new cards, if there is no linux driver, that recognizes it.

nvidia cards (or other brands with nvidia chips) often need the boot option nomodeset to produce some graphic output with the built-in nouveau driver. After that a proprietary driver can be installed in order to get the full performance of the nvidia graphics chip.

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I have nvidia graphics in two computers, I have added a card to a computer with already installed Ubuntu based operating systems, and it works for me. But I have no experience of the particular graphics card that you link to. Let us hope someone knows about that card, and can give advice about it.