Minecraft, FiveM, Rust, ARMA 3, ATS/ETS2 and Farming Simulator. Set up, modded and tuned to handle real players.
Getting a server online is the easy part. The real work is plugins that don't conflict, gamemode scripts that match what your community wants, and tuning so it stays smooth with fifty players on instead of the two you tested with.
Minecraft (Spigot, Paper, plugin development), FiveM (QBCore, ESX, Lua scripting), Rust (Oxide/Carbon plugins), ARMA 3 (missions and mod config), plus dedicated ATS/ETS2 and Farming Simulator co-op servers.
A server that's documented, not just running. What's installed, what it depends on, and how to update it without breaking anything.
Tell us what you're running and we'll let you know what it takes.