System Preparation
Valheim requires SteamCMD and 32-bit libraries.
Install dependencies:
sudo dpkg --add-architecture i386 sudo apt update sudo apt install -y steamcmd lib32gcc-s1
Run via systemd:
Create /etc/systemd/system/valheim.service with Type=simple and enable auto-start.
Note: Open UDP ports 2456–2458 in your firewall!