Open Steam and open the Settings > Controller > General Controller Settings
Turn on (Tick) all the Configuration Supports.
Close that window and close the Steam Settings window
(Or go to Desktop configuration to adjust how the controller acts when steam is running but not in a game)
Download the latest GloSC installer from https://github.com/Alia5/GloSC/releases
(Chromium based browsers may state that the program is dangerous, it is perfectly safe. I use it if that is of any comfort).
Run the GloSC installer to install GloSC. Open GloSC once installed
Click “Create New”
Type "Minecraft Dungeons" into the Name textbox.
Copy and Paste the below text into the Path textbox:
Ensure that “Launch game” has been enabled (ticked)
Click Save > Add to steam.
When steam restarts, a Minecraft Dungeons steam shortcut should be visible in the steam library.
(I can provide images to make the shortcut look pretty)
Just a few things to point out
Whenever you close the game, make sure to close the GloSC overlay
If your screen goes completely black use ALT-TAB to switch to the GloSC overlay and ALT-F4 to kill it (with kindness of course) then open the steam shortcut again but close the extra Game window that appears
Make sure to launch the game through “Desktop Steam” not big picture mode