Yes, it fully works for me!
Terminal:
system_profiler SPDisplaysDataType
Output:
macOS 26:
Displays:
LG HDR WQHD+:
Resolution: 6400 x 2666
UI Looks like: 3200 x 1333 @ 120.00Hz
macOS 27:
Displays:
LG HDR WQHD+:
Resolution: 7680 x 3200
UI Looks like: 3840 x 1600 @ 120.00Hz
144 Hz works as well.
I had to undo some of my previous configurations (0: disabled, 2: default)
defaults -currentHost write -g AppleFontSmoothing -int 2
Apple lists ultrawide display support as a feature:
Ultrawide display support. Now you can get higher resolutions on ultrawide displays, such as 5K at 120Hz. And your display arrangements stay exactly as you left them, for a seamless experience every time you plug in.
Copied from:
https://www.apple.com/os/macos/Previous discussion about macOS 26 Problem:
https://news.ycombinator.com/item?id=47569502