So after reading carefully through everything again, i actually managed to fix the issue!
As i noted in the first post, when i change my `ig-platform-id` to 01660003 HDMI does work.
So with the help of FBPatcher i found out which id belongs to which productname.
01660003 --> MacBookPro9,2 (issues built-in screen)
01660004 --> MacBookPro9,1 (no HDMI)
On the original guide in the second post there are framebuffer dumps, when taking a closer look at the two productnames it was easy to determine the difference.
MacBookPro9,1
05030000 02000000 30020000
MacBookPro9,2
05030000 02000000 30000000
02050000 00040000 07040000
03040000 00040000 81000000
04060000 00040000 81000000
So every buffer line seems to be for 1 port, so that means the first line is the built-in display.
This means that `05030000 02000000 30020000` works and `05030000 02000000 30000000` does not.
So at the end what i did was change my `ig-platform-id` to 01660003 (MacBookPro9,2) and add a find / replace patch for the first line:
View attachment 362142
Now, just for the sake of keeping things in order i disabled the ports that are not being used and i changed the connection type to HDMI (even though it worked as DP as well!?)
Cheers and thanks for your time.