How-to: Install RetroDECK on the Linux Desktop

Prerequisites

Ensure you have flatpak support installed on your Linux desktop. Follow the official flatpak guides for your distribution: Flatpak Setup Guide.
Install the steam-device package for udev rules for various controllers (most gaming focused distribution have this already). Check your distribution's instructions for how to install it.
It's recommended to add and launch RetroDECK from Steam to utilize the Steam Input feature for external controllers.

RetroDECK Installation

From the Desktop

Open your flatpak-supported software manager (e.g., GNOME Software for GNOME, KDE Discover for KDE).
Search for RetroDECK and press install.

From the terminal

Run the following command:

flatpak install Flathub net.retrodeck.retrodeck

First Run - Quick Start

Start RetroDECK for the first time
Choose where RetroDECK should create the main folder retrodeck/: Internal Storage, SD Card or Custom Location.
Put the BIOS files inside retrodeck/bios/.
Put the ROMs & game files inside retrodeck/roms/.
Choose to install Steam Controller Templates for RetroDECK (this should be checked by default) during installation.
Add RetroDECK to Steam: How-to: Add RetroDECK to Steam.
Enable controller support in Steam: How-to: Enable Controllers in Steam .
Connect your controller to your desktop.
Navigate to RetroDECK in Steam
Go to 🎮 Controller Settings -> Controller Layouts -> Templates and enable the template for the controller you are using.
Launch RetroDECK and enjoy!

Other Tips

Check on: How-to: Update RetroDECK.
If you no longer want RetroDECK, you can find the removal guide at: How-to: Remove RetroDECK.

Game Mode on Your Linux PC?

You can utilize Steam Deck's Game Mode on your Linux PC if your distribution supports it and specific hardware requirements apply for Game Mode to work.

It mitigates several issues with Steam Input and provides the best RetroDECK experience and playing Steam games with controllers out of the box.

Here is a list of some distributions that support Game Mode:

Bazzite

Bazzite Webpage

Bazzite: Steam Game Mode

Chimera OS

Nobara