I’ve had a server running without whitelist because a friend hadn’t bought the game yet, within 2 weeks it was griefed. It was just the two of us playing.
There are crawler bots just searching for unprotected Minecraft servers and it’s just a matter of time before they find yours.
It’s a shame the server lacks a pretty basic feature such as password protection.
This is the old SteamOS from over a decade ago and isn’t usable anymore. The modern SteamOS from the Steam Deck isn’t available yet for desktops.