I have the same issue. I’m not 100% sure if it’s related but would be happy to send any logs/info needed. My setup is slightly weirder, as I am running two external monitors via a USB-C dock. It used to work in my previous Fedora+Gnome setup, so it’s not the dock itself/cables/monitors.
However, in Plasma 6.2.5 the third monitor did not work at all; now in Plasma 6.3 I can get both to light up but only in this config:
- eDP-1 integrated display: 1920x1080, max: 1920x1080
- DP-3 Dell monitor: 2560x1440, max: 2560x1440
- DP-5 Philips monitor: 1920x1080, max: 2560x1440
Idk if it helps, but this is the output of kscreen-doctor:
$ kscreen-doctor -o
Output: 1 eDP-1
enabled
connected
priority 2
Panel
Modes: 1:1920x1080@60*! 2:1280x1024@60 3:1024x768@60 4:1280x800@60 5:1600x900@60 6:1368x768@60 7:1280x720@60
Geometry: 2560,360 1920x1080
Scale: 1
Rotation: 1
Overscan: 0
Vrr: incapable
RgbRange: Full
HDR: incapable
Wide Color Gamut: disabled
ICC profile: none
Color profile source: EDID
Color power preference: prefer efficiency and performance
Brightness control: supported, set to 90% and dimming to 100%
Output: 2 DP-3
enabled
connected
priority 3
DisplayPort
Modes: 8:2560x1440@60! 9:1920x1080@60 10:1920x1080@60* 11:1920x1080@60 12:1920x1080@50 13:1280x1440@60 14:1680x1050@60 15:1280x1024@75 16:1280x1024@60 17:1440x900@60 18:1280x960@60 19:1280x720@60 20:1280x720@60 21:1280x720@60 22:1280x720@50 23:1024x768@75 24:1024x768@70 25:1024x768@60 26:832x624@75 27:800x600@75 28:800x600@72 29:800x600@60 30:800x600@56 31:720x576@50 32:720x576@50 33:720x576@50 34:720x480@60 35:720x480@60 36:720x480@60 37:720x480@60 38:720x480@60 39:640x480@75 40:640x480@73 41:640x480@67 42:640x480@60 43:640x480@60 44:640x480@60 45:720x400@70
Geometry: 4480,360 1920x1080
Scale: 1
Rotation: 1
Overscan: 0
Vrr: incapable
RgbRange: Automatic
HDR: incapable
Wide Color Gamut: incapable
ICC profile: none
Color profile source: sRGB
Color power preference: prefer efficiency and performance
Brightness control: supported, set to 100% and dimming to 100%
Output: 3 DP-5
enabled
connected
priority 1
DisplayPort
Modes: 46:2560x1440@60*! 47:2048x1080@60 48:2048x1080@24 49:1920x1080@60 50:1920x1080@60 51:1920x1080@50 52:1600x1200@60 53:1280x1024@75 54:1280x1024@60 55:1152x864@75 56:1280x720@60 57:1280x720@60 58:1280x720@60 59:1280x720@50 60:1024x768@75 61:1024x768@60 62:800x600@75 63:800x600@60 64:720x576@50 65:720x576@50 66:720x480@60 67:720x480@60 68:720x480@60 69:720x480@60 70:640x480@75 71:640x480@60 72:640x480@60 73:640x480@60 74:720x400@70
Geometry: 0,0 2560x1440
Scale: 1
Rotation: 1
Overscan: 0
Vrr: incapable
RgbRange: Automatic
HDR: incapable
Wide Color Gamut: incapable
ICC profile: none
Color profile source: sRGB
Color power preference: prefer efficiency and performance
Brightness control: supported, set to 100% and dimming to 100%