Choosing Your Server Software
The Software tab for Project Zomboid only has the Public branch — there are no alternate branches to switch between. Any update applied here requires a server restart, and the dashboard will warn you before applying it.
Default Server Configuration
New Project Zomboid servers ship with a default Spawnly.ini configuration file, preset with Public=true (visible in the public server browser) and MaxPlayers=16. You can open and edit this file directly through the File Manager to change visibility, player limits, and other server settings — there's no separate Properties or World tab for Project Zomboid, since those only exist for Minecraft.
Next steps
For how to add Steam Workshop mods through this same file, see Installing Mods on Project Zomboid. Since Project Zomboid's persistent world state lives entirely in save files on disk, it's worth setting up Managing Backups & Restoring Your Server once your Spawnly.ini settings are dialed in.