Hello I have a Mac pro from 2008 can I install the latest Radeon graphics card on it ?

Also the RX 400/500 series cards require SSE4.2 CPU instruction support. Even if you did hack an OS upgrade those drivers would still crash because the 2008 Mac Pro CPU is too old.

The Radeon HD 7950 is the newest radeon card that will work. The Mac Edition variants works with bootscreen, generic PC cards work without a bootscreen.

Drivers for that card first appeared in MacOS Sierra 10.12.6. It does not appear to be flashable, so you get no boot-up screens: no startup manager, no recovery, no diagnostics, no Installer, no Safe mode, and no picture at all until the login screen appears after the driver has loaded.

There are better choices.

Your Mac is limited to 10.11 El Capitan, unless you use some hobbyist hacks to push it farther. Since these have a some potential for damaging your computer or yourself, we can not provide details here.

You can certainly insert it in your mac, but you will need to check to see if it can run in Mac OS X El Capitan,

or whichever older OS you are running on your Mac Pro.

Which Radeon card are you thinking of using.

Not allowed to discuss unsupported 'hacks' here. It is in the T&C's.

I think the RX 570 will not be detected by Mac OS X El Capitan.

You may have to find the answers you seek elsewhere.

It's is not a hack to ask, the hack is installing an OS on an unsupported mac.

We are not allowed to discuss hacking the OS or mac, you would

need to read the EULA for the macOS to see if it is legal or not.

YOU did not get scolded for asking the question -- ask away.

Readers apologized for not being able to provide you with the additional information, because of Terms of Use agreement.

That information is readily available on the internet, but we cannot post direct links to it, or they will be removed.

Now you are just rambling.