It means search and message input are unavailable inside that overlay mode; it does not mean Discord chat is disabled everywhere.
What To Do
Switch to the Discord app outside the game to search or send messages.
The copy does not provide a specific overlay-setting change, so no unconfirmed compatibility tweak is presented as a fix.
Search Intent
Searchers likely want to know why search or typing fails in the Discord game overlay, whether the keyboard is broken, and how to send a message instead.
Related Phrases
Discord Overlay
compatibility mode
keyboard input
Search unavailable
Typing is unavailable
switch to Discord
Evidence
All three strings were added together, and the detailed notice explicitly connects compatibility mode, blocked keyboard input, and switching to Discord outside the game.
Confidence
high
Current Value
The overlay is running in compatibility mode for this game and cannot receive keyboard input. Switch to Discord outside of the game to send messages.