Black screen on Steam Deck when switching to Desktop Mode with external display connected

[abstractrealism]

Your system information

• Steam client version: 1763795278
• SteamOS version: 3.7.17
• Opted into Steam client beta?: No
• Opted into SteamOS beta?: No
• Have you checked for updates in Settings > System?: Yes

Please describe your issue in as much detail as possible:

When switching to Desktop Mode with the steam deck docked and connected to an external display, upon arriving in Desktop Mode only the external monitor will have anything on it. The Deck's internal monitor will be lit up but all black. This is mostly an issue as the Start Menu (I'm sure that's not what you actually call it) and taskbar etc are all being sent to the Deck's monitor, and thus inaccessible. If I unplug my dock, switch to desktop mode, then reconnect it, everything works fine.

Steps for reproducing this issue:

1. With Steam Deck docked via a USB C to HDMI + USB A hub (3rd party, not the official one) switch to desktop mode. A mouse and keyboard are the only other things I have plugged in usually.
2. In Desktop Mode, the external HDMI monitor (Asus ProArt 27" 1080p, if it matters) will work perfectly, the Deck's internal monitor will not have anything on it.