I setup a Minetest server on my Raspberry Pi few years back but I never actually used it. Now, I want to recreate my server, since Minetest has released version 5.2.0.
This guide is just my own experience following the wiki page on setting up a server and reading on the minetest forums.

Install the dedicated minetest server package for your operating system. For Debian it will be: $ sudo apt install minetest-server
Use the buster-backports branch to get the latest version of Minetest:
To check the version avaiable:

$ apt-cache policy minetest-server
  Installed: 5.2.0+repack-1~bpo10+1
  Candidate: 5.2.0+repack-1~bpo10+1
  Version table:
 *** 5.2.0+repack-1~bpo10+1 100
        100 http://httpredir.debian.org/debian buster-backports/main amd64 Packages
        100 /var/lib/dpkg/status 500
        500 http://httpredir.debian.org/debian buster/main amd64 Packages

Stop the Minetest Server:
$ sudo systemctl stop minetest-server

If you have played Minetest on your desktop or laptop using Debian or other similar GNU+Linux Operating System, you can just use your existing world, game and mod to be the server.

Copy the directory from your laptop/desktop ~/.minetest, this path will be: /home/yourusername/.minetest. Copy that to your server machine/var/games/minetest-server/`, I will be using my HP T610 for hosting the Minetest Server.

Change ownership to Debian-minetest$ sudo chown -R Debian-minetest:games /var/games/minetest-server/.minetest

Tweak the settings of your minetest server:
Edit the file: minetest.conf

default_game = mineclone2

# Admin name
name = r1bnc

# Server stuff
# Network port to listen (UDP)
port = 30000

# Bind address
bind_address =

# Name of server
server_name = My Minetest server

# Description of server
server_description = Minetest server powered by 
# Message of the Day
motd = Welcome to Minetest. Enjoy your stay!

# Maximum number of players connected simultaneously
max_users = 5

# Whether to enable players killing each other
enable_pvp = true

# Set to true to enable creative mode (unlimited inventory)
creative_mode = true

# Enable players getting damage and dying
enable_damage = true
ipv6_server = false

# Location of existing world from your previous plays of minetest
map-dir = /var/games/minetest-server/.minetest/worlds/rand

# Optimizations, see References
max_block_send_distance = 8
max_simultaneous_block_sends_per_client = 5
active_block_range = 2
server_map_save_interval = 10.3

Start your Minetest Serve:
$ sudo systemctl start minetest-server

Connect to your server using the Minetest Client from your PC or Android:

Allow UDP port 3000 to your firewall if you have problems.