If your game uses wine with DXVK, then see post #4. For other wine games, you can only have output on the terminal with the +fps option
You could also try to add non-steam games in steam. Maybe you'll be able to use the steam overlay then.
]]>export DXVK_HUD=fps
This work for me on wine games.
]]>GALLIUM_HUD=fps wine game.exe
If you use steam, then there may be some sort of steam overlay with fps available.
]]>