Step 0: Prerequisites

L4T Ubuntu

That's it, all the other prerequisites are automatically installed for you when you install MCSwitchTools for the first time.

Step 1: Downloading MCSwitchTools
Download the latest version of MCSwitchTools from the release folder.
Extract the file you downloaded and make sure the name of the extracted folder is MCSwitchTools. If it is not named that, rename it.
Move this folder to your home folder.

Step 2: Installing MCSwitchTools
Open Terminal from either the launcher or by using the key combination Control+Alt+T.
Run these commands inside Terminal; enter your password if it prompts you for it:
sudo apt update
~/MCSwitchTools/tools.sh init
After running those commands, restart Terminal.

Step 3: Selecting your LWJGL version
Now, you need to choose a LWJGL version. The options are 2 or 3. If you plan on using Minecraft 1.13+, choose 3. If you plan on using Minecraft 1.12.2 or below, choose 2. You can change this at any time.
To choose your LWJGL version, simply run this command inside Terminal:
mc lwjgl (2 or 3)
If you're not sure which version to choose, just choose 3:
mc lwjgl 3

Step 4: Running the launcher and fixing your profiles
It's finally time to start the Minecraft launcher. Run this command to run the launcher:
mc run
Once the launcher opens, log in to your Mojang or Minecraft account then close the launcher.
For Minecraft to actually work, you'll need to run this command:
mc profiles
Any time you add a new launcher profile (for OptiFine, Forge, etc.), you'll need to run that command to prevent Minecraft from crashing.

Step 5: Starting Minecraft
Any time you want to play Minecraft, you'll have to run this command in Terminal:
mc run
After all the previous steps have been completed, you can run that command and play Minecraft as you normally would. Enjoy!
It is highly recommended that you check out the 'Tips' section below to get better FPS when playing Minecraft, though it is not necessary.