adoptium.net VS Purpur

1.18 requires Java 17. (Java link if you need it)

Note: In order for JarFix to work, you needed add all options when installing Java (Picture).

Did you actually install a Java Development Kit? Because this sounds like you only installed a text editor. You can download it here: https://adoptium.net/ (download the latest version for your OS and install it)

Try this https://adoptium.net/

Make sure you have Java fully installed (select all components when installing). Link to Java download if you need it: (Link)

if you downloaded Java from adoptopenjdk/adoptium/temurin/whatever they call it now, you do have it.

I had the same issue and I fixed it with downloading openjdk 17. you can download it here https://adoptium.net/

Which was recently rebranded as Eclipse Temurin

if they are using Windows, have them reinstall java https://adoptium.net/

e.g https://adoptium.net/

We will be downloading the Minecraft server files into this directory. To preface, there are numerous variations of server JARs that can be used (e.g. Spigot, Paper, Purpur each touting their own benefits). For this tutorial, we will be working with Paper, a fork of Spigot that is optimized for performance.

I Mostly Like Linux as a OS For a Server and PurpurMC (https://purpurmc.org) As a Server Software and i Mostly Use EssentialsX and WorldEdit and More Server Management Stuff.

If you prefer to go the old-school Bukkit/Spigot/Paper/Purpur route (which provides the greatest level of compatibility with pre-existing server plugins), I recommend the latter of the four. Each of these projects is a fork, built on each other in that same order. Each fork offers additional customisation, API, and performance enhancements over its predecessor.

I’d recommend Paper (which is a fork of spigot) or Purpur which is a fork of paper and pufferfish

If you're looking to re-add gravity duping I would recommend not using a plugin but switching your server software to PurpurMC. It is a fork/version of PaperMC that re-adds gravity duping as a config option as well as the ability to toggle back on things like tnt duping and several other features that the PaperMC devs arbitrarily decided were bugs (even though Mojang has explicitly not removed them).

Small addendum:\ If you want to keep using a paper derivative (as a drop-in replacement), you can use purpurMC instead. It provides a config option to enable gravity block duping by disabling sand.fix-duping. (At least for sand)

You can host a small purpur server

Have you tried re-downloading the latest purpur jar file from the purpur website?

tweak some configuration, try lower your entities spawn, I at last you might want to try PurPurMC for the server, it's paper fork with some modification, I feel a lot of improvement since using this fork...