[16:59:13] [Server thread/INFO]: [LuckPerms] Loading LuckPerms v5.2.35

[43,552s][warning][os,thread] Failed to start thread - pthread_create failed (EAGAIN) for attributes: stacksize: 1024k, guardsize: 0k, detached.
[43,553s][warning][os,thread] Failed to start thread - pthread_create failed (EAGAIN) for attributes: stacksize: 1024k, guardsize: 0k, detached.
[43,554s][warning][os,thread] Failed to start thread - pthread_create failed (EAGAIN) for attributes: stacksize: 1024k, guardsize: 0k, detached.
[43,556s][warning][os,thread] Failed to start thread - pthread_create failed (EAGAIN) for attributes: stacksize: 1024k, guardsize: 0k, detached.
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by me.lucko.luckperms.common.dependencies.classloader.ReflectionClassLoader (file:/home/MiniPixel-1.16.4/plugins/LuckPerms-Bukkit-5.2.35%20(3).jar) to method java.net.URLClassLoader.addURL(java.net.URL)
WARNING: Please consider reporting this to the maintainers of me.lucko.luckperms.common.dependencies.classloader.ReflectionClassLoader
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
[16:59:13] [ForkJoinPool-3-worker-17/WARN]: java.lang.OutOfMemoryError: unable to create native thread: possibly out of memory or process/resource limits reached
[16:59:13] [ForkJoinPool-3-worker-17/WARN]: at java.base/java.lang.Thread.start0(Native Method)
[16:59:13] [ForkJoinPool-3-worker-17/WARN]: at java.base/java.lang.Thread.start(Thread.java:803)
[16:59:13] [ForkJoinPool-3-worker-17/WARN]: at java.base/java.util.concurrent.ForkJoinPool.createWorker(ForkJoinPool.java:1329)
[16:59:13] [ForkJoinPool-3-worker-17/WARN]: at java.base/java.util.concurrent.ForkJoinPool.tryAddWorker(ForkJoinPool.java:1352)
[16:59:13] [ForkJoinPool-3-worker-17/WARN]: at java.base/java.util.concurrent.ForkJoinPool.signalWork(ForkJoinPool.java:1476)
[16:59:13] [ForkJoinPool-3-worker-17/WARN]: at java.base/java.util.concurrent.ForkJoinPool.deregisterWorker(ForkJoinPool.java:1458)
[16:59:13] [ForkJoinPool-3-worker-17/WARN]: at java.base/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:193)
[16:59:13] [ForkJoinPool-3-worker-51/INFO]: [LuckPerms] It is safe to ignore any warning printed following this message starting with 'WARNING: An illegal reflective access operation has occurred, Illegal reflective access by me.lucko.luckperms.common.dependencies.classloader.ReflectionClassLoader'. This is intended, and will not have any impact on the operation of LuckPerms.
[16:59:13] [ForkJoinPool-3-worker-3/WARN]: java.lang.OutOfMemoryError: unable to create native thread: possibly out of memory or process/resource limits reached
[16:59:13] [ForkJoinPool-3-worker-3/WARN]: at java.base/java.lang.Thread.start0(Native Method)
[16:59:13] [ForkJoinPool-3-worker-3/WARN]: at java.base/java.lang.Thread.start(Thread.java:803)
[16:59:13] [ForkJoinPool-3-worker-3/WARN]: at java.base/java.util.concurrent.ForkJoinPool.createWorker(ForkJoinPool.java:1329)
[16:59:13] [ForkJoinPool-3-worker-3/WARN]: at java.base/java.util.concurrent.ForkJoinPool.tryAddWorker(ForkJoinPool.java:1352)
[16:59:13] [ForkJoinPool-3-worker-3/WARN]: at java.base/java.util.concurrent.ForkJoinPool.signalWork(ForkJoinPool.java:1476)
[16:59:13] [ForkJoinPool-3-worker-3/WARN]: at java.base/java.util.concurrent.ForkJoinPool.deregisterWorker(ForkJoinPool.java:1458)
[16:59:13] [ForkJoinPool-3-worker-3/WARN]: at java.base/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:193)

When I start my server this the error message the console is sending.

If you have this same error, @zbw818, please open a new issue and fill out the form as detailed as possible rather than commenting on old, closed issues.

Looks like your server hardware just doesn't have enough thread to work with. But in any case, follow the issue template.

What would be enough thread?

It varies, but usually at least 1000 are available - likelihood is that something is using lots of them up.

However, that error is unrelated to the LP error message. That is fixed by updating to a newer version: https://luckperms.net/download