MacBook Air M3 with two monitor setup using HP Thunderbolt Dock G4

WheelieNick wrote:

Have you put the Mac in clamshell mode? This is nessecary to get it working. I have it working, but without a dock, just with 2 usb c cables to the different monitors

This is the key point. The M3 MacBook Air supports two external displays only in clamshell mode (external keyboard/mouse and AC power).

From the specs:

Simultaneously supports full native resolution on the built-in display at 1 billion colors and:

• One external display with up to 6K resolution at 60Hz
• Close the MacBook Air lid to use a second external display with up to 5K resolution at 60Hz

Timo Ruohomaki wrote:

Yes, that's what I meant by "working with two external displays, lid closed". I have tried connecting it both on the USB-C and USB-C/TB ports while lid closed and also while open but then shutting the lid.

Here are Apple's instructions, note the order of 3-5 (which sounds different than what you state):

1. Connect an external keyboard and mouse or trackpad.
2. Connect the Mac to power. If the external display provides power to the Mac, a separate power adapter isn’t needed.
3. Connect the first display. This will be the primary display, supporting up to 6K resolution at 60Hz (or 4K at 144Hz).
4. Close the laptop lid.
5. Connect the second display. This will be the secondary display, supporting up to 5K resolution at 60Hz (or 4K at 100Hz).

Have you put the Mac in clamshell mode? This is nessecary to get it working. I have it working, but without a dock, just with 2 usb c cables to the different monitors

There is no point in installing DisplayLink drivers unless you are using a DisplayLink-equipped device.

Thunderbolt docks usually do not use DisplayLink and similar second-class "workarounds". They tend to rely upon hardware video output from the computer.

The HP Thunderbolt Dock G4 is a Thunderbolt 4 dock that supports up to four 4K displays. It has four video output ports: a HDMI 2.0 port, two DisplayPort 1.4 ports, and a USB-C (DisplayPort Alt Mode) port. I suspect that the dock is using something akin to DisplayPort MST daisy-chaining to provide four video outputs - instead of the usual two.

Macs do not support DisplayPort MST daisy-chaining, and so it is my. suspicion that this dock can only support two displays when used with a Mac, and that the particular combination of video outputs you use might matter.

In the Q&A section on the HP site, someone had asked "Q: Does this have a DisplayPort MST hub inside that drives the two displays? Mac systems do not support DisplayPort MST, so my Mac will only recognize the presence of a single display and both displays will mirror each other,", but there was no answer.