I am experiencing a similar issue and have tried various suggestions mentioned in this thread. However, my external monitor continues to flicker. Below are the details of my setup:
Display: LG 27UL650-W
Adapter: Apple USB-C Digital AV Multiport Adapter
macOS: 14.4.1 (Sonoma)
Chip: Apple M3 Pro
Device: MacBook Pro
RAM: 18GB
When I connect the monitor directly to the HDMI port of the MacBook, it works fine. However, when I use the adapter, the screen flickers. To isolate the issue, I have experimented with various configurations:
I used the same adapter and monitor with my iPad Pro, and the setup worked fine without any flickering. This confirms that both the monitor and the adapter are functioning correctly.
I attempted to switch between the three USB-C ports on the MacBook, but the problem persisted across all ports.
I tried connecting and disconnecting power to the USB-C slot on the adapter, but the issue remained unchanged.
As a temporary solution, I am reverting to using the native HDMI port on the MacBook. However, this defeats the purpose of purchasing the adapter, as I intended to use it as a dock. Moreover, having the HDMI on the right side is less convenient for me; I would prefer to connect everything from the left side. It would be greatly appreciated if Apple could reproduce this issue and address it in an upcoming release.