Can I install Asus Radeon RX 570 for an update to Mojave on my Mac Pro Mid 2012?

It should work just fine, provided you have the correct power cables. Apple has a list of supported cards that can be found here.

Hope it helps!

-Geotrax

"No boot screens" with a non-Mac-Edition card may present a problem getting Mojave installed. If you use the old card, Mojave will not install. If you use the new card, you may not get the screens allowing you to answer the questions to make the install happen.

If you find yourself in that situation, there is a way you can leverage your existing genuine old Mac-firmware card to get Mojave Installed, then switch over to the new card. That is to use a hobbyist hack (generally used to install on non-conforming Macs), but do not request any special add-ons, since your Mac will work fine once the new card is in. This hack installs a Metal software-emulator that works with the 5770 and other genuine Mac-firmware cards (I tried it with my 5770 and it works except a few tab bars are dark gray at times in light mode).

This hack is not supported or endorsed by Apple, and if you get your machine in a wonky state, you have to "think like a developer" to get it out and working again. If you are strictly creative, this is much too risky to try. You can find it easily by searching for dosdude and Mojave patcher.

Are you starting from MacOS 10.13.4? You need to have run 10.13.4 at least once previously to get all the processor firmware updates.

Is the old graphics card is in the machine when you do this? Is it a genuine Mac-firmware card?

You can try again or email the developer and see if he can help.

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If you can get Mojave installed, all the drivers will be there, you just swap in your new card and its driver will be selected at Startup.

"No boot screens" with a non-Mac-Edition [and Metal-2 capable] card may present a problem getting Mojave installed.

-- If you use the old card, Mojave will not install.

-- If you use the new card, you may not get the screens allowing you to answer the questions to make the install complete.

Mojave Patcher is a way around the requirement that you have the new card installed. It is not supported, and Apple likely does not approve of it. The release document runs 15 printed pages, and needs to be followed fairly religiously to be successful.

Apple will tell you to use a Mac-Edition card.

what graphics card are you using now?

could you have both installed, or not (based on aux power cables) ??