Dell Latitude 5491: HDMI not working

[Hervé]

Did you try and experiment with other CFL mobile framebuffers?

 

For instance FB 0x3EA50004:

ID: 3EA50004, STOLEN: 57 MB, FBMEM: 0 bytes, VRAM: 1536 MB, Flags: 0x00E30B0A
TOTAL STOLEN: 58 MB, TOTAL CURSOR: 1 MB (1572864 bytes), MAX STOLEN: 172 MB, MAX OVERALL: 173 MB (181940224 bytes)
Model name: Intel Iris Plus Graphics 655
Camellia: CamelliaV3 (3), Freq: 0 Hz, FreqMax: 0 Hz
Mobile: 1, PipeCount: 3, PortCount: 3, FBMemoryCount: 3
[0] busId: 0x00, pipe: 8, type: 0x00000002, flags: 0x00000498 - ConnectorLVDS
[1] busId: 0x05, pipe: 9, type: 0x00000400, flags: 0x000003C7 - ConnectorDP
[2] busId: 0x04, pipe: 10, type: 0x00000400, flags: 0x000003C7 - ConnectorDP
00000800 02000000 98040000
01050900 00040000 C7030000
02040A00 00040000 C7030000

or 0x3EA50006:

ID: 3E9B0006, STOLEN: 38 MB, FBMEM: 0 bytes, VRAM: 1536 MB, Flags: 0x00131302
TOTAL STOLEN: 39 MB, TOTAL CURSOR: 512 KB, MAX STOLEN: 39 MB, MAX OVERALL: 39 MB (41422848 bytes)
Model name: Intel UHD Graphics 630
Camellia: CamelliaV3 (3), Freq: 0 Hz, FreqMax: 0 Hz
Mobile: 1, PipeCount: 1, PortCount: 1, FBMemoryCount: 1
[0] busId: 0x00, pipe: 8, type: 0x00000002, flags: 0x00000498 - ConnectorLVDS
00000800 02000000 98040000

Latter would need to be patched for 3 ports and injection of con1+con2 as additional connectors of course.

 

Or change con1/con2 flags of FB 0x3EA50009 from C7010000 to 87010000 or C7030000?

 

Try and post an IOReg extract when HDMI is plugged in.