Big Sur doesn't support 5K on Dell UP2715K monitor

[Squuiid]

It would appear as though Big Sur no longer supports the 5K Dell UP2715K monitor. This is an MST monitor which requires two DisplayPort cables to function in 5K.

Catalina and Mojave worked just fine, and indeed had a profile built in for this monitor.
It worked on both integrated Intel gfx as well as an RX5700XT eGPU on a 2018 Mac mini.
It also worked fine on a 2019 16" MacBook Pro.

Big Sur 11.0.1 will now only display a maximum resolution of 4K, and defaults to 1440p. It will not register the second DisplayPort cable to make MST work.

Anyone else have any luck with the Dell UP2715K monitor in 5K on Big Sur?

 

[Squuiid]

UPDATE: This is a non-issue.
I had tried powering the monitor off using the switch on the side and then powering back on. Apparently this wasn't good enough.
This time I removed the power cord and then plugged back in and 5K started working again. Odd that it coincided with the Big Sur upgrade but purely coincidental and nothing more.

Apologies for the misleading article. Clearly this is a firmware bug with the Dell.

 

[Medo12223]

Hello
I’m using Dell 5k up2715 too , I was able to run in 5k resolution with Catalina , and Mojave I was using clover
Currently using opencore , but I cannot drive it in 5k , can you help me please ?
Are you using clover or opencore , and can you share your EFI , please ?

 

[Squuiid]

Hi, I’m using it on the Mac mini so neither.
The Mac Pro is best left on Mojave as far as I’m concerned 😬