ServerStarterJar and Forge 1.20.2|1.20.3

[Griefed]

Issue

The NeoForge project's ServerStarterJar appears to have compatibility issues with Forge for MC 1.20.2 and 1.20.3. That, or something within Forge itself is borked, though I believe it to be a compatibility issue because Forge changed something in those versions.

You may encounter errors similar, but not exactly the same, as the follwing:

Other versions were tested and found to be working:

MC 1.20.1, Forge 47.3.11 works
MC 1.20.4, Forge 49.1.12 works
MC 1.20.5 has no Forge support
MC 1.20.6, Forge 50.1.20 works
MC 1.21, Forge 51.0.33 works
MC 1.21.1, Forge 52.0.16 works

Workaround

As of 7.1.0 users can change USE_SSJ in the variables.txt using true|false.
This toggle only affects Forge and is useful if Forge versions are incompatible with the ServerStarterJar. Turning USE_SSJ off will ensure the start scripts use the classic way of installing and starting a Forge server.

Workaround for start scripts generated with SPC prior to 7.1.0

For Forge 1.20.2, a workaround would be using the start-scripts generated by ServerPackCreator to install the server and all the files which come with said installation. With said installation, run.bat and run.sh-scripts are generated. These are the default barebones start scripts Forge provides.
As the ServerPackCreator start scripts create the user_jvm_args.txt used by the run.xx-scripts, you should then use the run.xx-scripts as a workaround for Forge 1.20.2 server packs.

In short, the workflow becomes:

1. Use ServerPackCreator start-scripts to install the Forge 1.20.2 server and files
2. Once it crashes with an error similar to the ones above, use the run.xx-script appropriate for your system (bat for Windows, sh for Linux)
3. ???
4. Profit

Forge for 1.20.3

Forge 1.20.3 appears to have a different issue with the ServerStarterJar, further strengthening the believe that the issue above was caused by a change on Forge's side of things.

The installation for Forge 1.20.3 barely works. The run-scripts aren't generated, so you can use the workaround with scripts generated by 7.1.0 or newer.

I recommend using the old-school way of installing Forge 1.20.3: https://minecraft.fandom.com/wiki/Tutorials/Setting_up_a_Minecraft_Forge_server

Addendum

As this isn't an error related to ServerPackCreator, I won't spend time on working on a fix for this particular issue.

Though if possible, stay away from Forge for MC 1.20.2 and 1.20.3. Not sure what Forge changed, but apparently said changes didn't work as planned, so even Forge decided to take them back in newer versions, as 1.20.4 and up work fine, as do 1.20.1 and older.