Some days ago I asked for help.
This week I received my new purchase: NVIDIA Quadro NVS510 (4x displays).
I put it on my system and ... I got all my monitors working (3x), also on boot :).
But I did a fresh macOS Mojave install, following this guide, step by step, and everything is...
I'm from Portugal. Buying from US is not an option, unfortunately :( , because of customs taxes.
I will try to buy an Nvidea Quadro NVS510 (4x monitor and low power consuption, but future support in risk ?!?!?)
or AMD Rx570/580 (4x monitor, more power consuption, but better future compliance).
No I make it worst...
1st I tried some other cables and adapters that I've. Not many, but no difference.
2nd I realize that I had BIOS version A24 (I've updated it some time ago). So I updated to last one: A25.
After this, single monitor boot is OK, but now I connect the second monitor and it...
I did that, but not on boot screen. I change the SMBIOS from 14,2 to 14,3 directly in my config.plist file, and then rebooted. (did not redo the serial)
The problem persists. Just single monitor boots. But after the boot I can connect 2 monitors and they work.
I've been using my hackintosh (in a Dell 9020) with default HD4600 graphic card, and Mojave 10.14.5. I use it for software dev stuffs (no need for advanced GPU). But I love to use 2 monitors.
If I boot my PC with just one monitor connected and then after boot completed, connect the second...