Officially supported distros are CentOS 7 (x86_64), Debian 10 & 11 (amd64, arm64), openSUSE 15 (x86_64) and Ubuntu 18.04 through 22.10 (amd64).  Unofficially supported distros are Pop!_OS 20.04, Fedora 37 (x86_64) and Nobara 37 Official (x86_64).

Step 1: Install avrdude

This is technically only required if you plan on using the RetroSpy Pixel Updater, for use with the RetroSpy Pixel GameBoy Printer Emulator.

sudo rpm -Uvh epel-release*rpm
sudo yum install avrdude

Debian and Ubuntu
sudo apt-get install avrdude
Fedora and Nobara
sudo yum install avrdude
zypper install avrdude

Step 2: Give yourself permissions to the serial port

You will need to add your account to the group with permissions to the serial port, this is typically dialout.  This command below gives you the permissions you need: sudo usermod -a -G dialout $USER.  Theoretically you need to logout and log back on after adding yourself to the group, but I found I sometimes had to go as far as rebooting the machine for the permissions to take effect.

Step 3: (Optional) Adjust scaling

If you have a high dpi screen you will probably want to add the following line to the bottom of your .bashrc (or your preferred shell of choice’s config file), or else the RetroSpy window will be VERY tiny. Remember to logout and log back in for this to take effect.

Step 4: (Ubuntu 22.10 & Pop!_OS 20.04) Remove brltty

One of the braille display drivers that is installed by default in Ubuntu 22.10 has vendor/product ids that conflict with many Arduino boards, so unless you are using a braille display you will need to remove the brltty package in order to use RetroSpy.
sudo apt-get remove brltty

Step 5: Download the latest RetroSpy

Download and extract the latest version of RetroSpy.

tar -zxvf RetroSpy-Linux-x64.tar.gz
tar -zxvf RetroSpy-Linux-arn64.tar.gz

Step 6: Installation Complete

You can run bin/retrospy from the RetroSpy-Linux directory to start the main RetroSpy UI.  Also installed are the RetroSpy Pixel Viewer (bin/pixelview) and RetroSpy Pixel Updater (bin/pixelupdate), for use with the RetroSpy Pixel Gameboy Printer Emulator.  The last item installed is the RetroSpy Vision USB Updater (bin/visionusbupdate), for use with the RetroSpy Vision USB hardware.  On most machines the RetroSpy executables do not need to be run as root or with sudo, but we have encountered some installs that required running with elevated permissions.