

Set the Dell display refresh rate to 30 hertz.The only way I've been able to get the Dell display to work without flickering is:
My flicker pro#
I'm having the same issue.brand spanking new MacBook Pro 13' with touch bar connected via the Apple USB-C digital AV multiport adapter and HDMI cable to an equally brand spanking new Dell U3415W 34' curved display. It looks like this is a very old problem with Macbooks Pro, I have a MB Pro 13" mid 2012, and the same is happening right now, like ARM44 tells in this link : If it's being forced into any other refresh rate (like 30Hz), that could be the problem. Last but not least, a little shiny bird told me that 4K displays have to be configured for 60Hz to function correctly.

(And if you happen to have a second Mac other than the shiny new MacBook Pro 13" hanging around for testing, that would narrow it even further!) You could test with a different display like a TV to see if the issue still occurs.Have you ensured the expensive dongle for HDMI output isn't defective? You could try booting into - and back out of - Safe Mode. You could try a PRAM reset on the shiny new MacBook Pro 13" (if you haven't already).
My flicker update#
My flicker software#
Have you checked for software updates from the App Store since the first time you connected the expensive dongle for HDMI output?
