I was wondering, would it be possible to add either Server password or a Whitelist without using mods?
Legacy has whitelisting. I haven’t seen garry specifically post about it, but I imagine experimental will use the same system if it isn’t implemented already: Membership in a specified Steam group whitelists you, and it’s up to the group creator how membership in the Steam group works (invite only, public join, etc.).
Yeah, I remember Legacy had it, time will tell if we see this in Release too.