Tested and confirmed working on (As of July 20th 2020)

Ubuntu 16.04 LTS
Ubuntu 18.04 LTS
Debian 9
Debian 10

0. Install these prerequisites

sudo apt-get install screen htop unzip git                               # Usefull utilities
sudo apt-get install lib32stdc++6                                        # SteamCMD dependencies
sudo apt-get install mono-runtime mono-reference-assemblies-2.0          # Unity env
sudo apt-get install libc6 libgl1-mesa-glx libxcursor1 libxrandr2        # 64 bit prerequisites for Unity 3D
sudo apt-get install libc6-dev libgcc-4.8-dev                            # prerequisites for BattlEye

1. Download and extract files in your home dir

git clone https://github.com/gegtor/Unturned-64Bit-Server-Scripts
cp Unturned-64Bit-Server-Scripts/* ~/
rm -r Unturned-64Bit-Server-Scripts/ README.md

2. Set correct script permissions and allow them to execute

sudo chmod +x start.sh
sudo chmod +x update.sh

3. Install the game

./update.sh

4. Copy LDM module

cp -r Unturned_Server/Extras/Rocket.Unturned/ Unturned_Server/Modules/

5. Copy Steam lib just to be on the safe side

sudo cp Steam_CMD/linux64/steamclient.so /lib

6. Start your new server!

./start.sh <instance_name>
./start.sh server-1

7. To prevent server from being closed when exiting ssh session run it in screen

screen -S <screen_name>
./start.sh <instance_name>

screen -x <screen_name> to return to your screen

8. How to update?

./update.sh
Do step 4 to update LDM if necessary