When I setup a new project in Windows filesystem,
with the classpaths configured like this:
-cp C:\Users\foo\IdeaProjects\bar\build\classes\java\main;C:\Users\foo\IdeaProjects\bar\build\resources\main;C:\Users\foo\AppData\Roaming\Hytale\install\release\package\game\latest\Server\HytaleServer.jar
The server's asset loader puts the plugin pack at first slot, causing it to be the "default" assets pack, and the server crashes not being able to load basic assets.
I tested this on Linux under WSL2, and despite having the classpath order the same (plugin stuff first, game assets second), it doesn't do that.
The workaround is to add Hytale:AssetModule to plugin's dependencies in manifest.json
"Dependencies": {
"Hytale:AssetModule": "*"
},