The ATLAS Public Test Realm (PTR) is available to all players via the Steam beta branch. You can join the PTR by following these steps:
1. Right click on the ATLAS game in your steam library and select "Properties...".
2. Select the "BETAS" tab on the left.
3. Enter the following beta access code: PathfinderLifeForMe
4. Select the "test2021 - recruit testers" beta in the drop down box.
5. Close the window and launch ATLAS after it updates.
To opt back into the live version of the game, select the "None" beta in the drop down box.