WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by me.lucko.luckperms.common.dependencies.classloader.ReflectionClassLoader (file:/C:/Users/KendallCraft/Desktop/1.15.2%20Server/plugins/LuckPerms-Bukkit-5.1.26.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

[Server thread/INFO]: [LuckPerms] Loading LuckPerms v5.1.26
[23:08:56] [ForkJoinPool-2-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.

I mean it literally tells you...

It is safe to ignore any warning printed following this message

This is intended, and will not have any impact on the operation of LuckPerms

It also said to consider reporting it, so I did.