I am dual-booting a Steam Deck with SteamOS and Windows 11, and using the official dock with external monitors (or at least I'm trying).
Every SteamOS and dock firmware update is installed (stable channel, no beta or any preview update).
My main monitor is 1080p@75Hz, the secondary is 1080p@60Hz.
My problem is, that I can only use both the external monitors, at the same time, with full resolution and refresh rate in Windows 11. In SteamOS, only one external monitor is usable (either connected to the Displayport, or the HDMI). When I plug in the second monitor, Everything goes black, and nothing happens. When I unplug from either the HDMI or the Displayport, everything is fine.
The only time I can use both displays in SteamOS, is when I force booting into desktop mode by default, and both monitors are already connected to the dock, before turning the Deck on. In this case, however the monitor connected to the Displayport only has a few 4:3 aspect ratio resolution options (even though both my monitors are FullHD 1080p)
I have already tried all the troubleshooting options from the official pages, with no luck.I have tried a Kubuntu live USB, which also has the same problem (also tried in Wayland session instead of X11, with the same results).I have also tried the dock with my work laptop, with Windows 10, and both monitor works correctly.So the hardware can do it, as far as I can confirm.
I think it is something to do with the Linux kernel, which might have been discussed in this Github topic:
https://github.com/ValveSoftware/SteamOS/issues/1399
Which concludes, that a later kernel version has some kind of fix for this.
Steam Support says, that "the dual-boot setup is interfering with the normal process"
Is there any chance I can make it work now, or I have to wait for a kernel update?