I'm running a dual-monitor setup. Initially, my primary display was connected through HDMI and the secondary one through DVI, but the second monitor didn't work. After connecting both displays through HDMI, they work together, but a problem appears when I set the main monitor to 240Hz: its brightness becomes extremely low and the brightness controls stop working. The main display works normally at 240Hz when the second monitor is disconnected, and both screens also look fine when they're set to 60Hz. This happens across multiple Linux distributions, including systems using Wayland, while the monitors work correctly under Windows. Is there a way to use 240Hz on the main monitor while keeping the second display at 60Hz?
2 Answers
This can be a display-server or graphics-stack limitation, especially with older X11 setups, since mixed refresh rates haven’t always been handled well. A current Wayland session with GNOME or KDE Plasma is usually the best place to start, but Wayland alone doesn’t guarantee that every monitor and driver combination will work correctly.
The behavior may depend on the specific distribution, desktop session, GPU driver, and monitor connection. Some systems handle mixed refresh rates correctly while others still have issues; for example, one setup had the problem on Bazzite but worked normally on CachyOS. Comparing the session type and graphics driver between those installations could help identify what differs.
I tested this on Fedora and CachyOS, which appeared to be using Wayland, but the brightness problem still happened.