Can't run jar on linux mint 20 64 bit.

[TheGuyWhoo]

WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.lwjgl.LWJGLUtil$3 (file:/home/nickelas/Downloads/pixel.jar) to method java.lang.ClassLoader.findLibrary(java.lang.String)
WARNING: Please consider reporting this to the maintainers of org.lwjgl.LWJGLUtil$3
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
Inconsistency detected by ld.so: dl-lookup.c: 111: check_match: Assertion `version->filename == NULL || ! _dl_name_match_p (version->filename, map)' failed!

I get that.

[SomeTroglodyte]

IMHO known Ubuntu issue (the loader error, the warnings are simply correct), not a PD one. Get another Java runtime - even pulling the exact same sources that are supposed to have been used for the official repo OpenJDK and compiling them yourself should work. I normally use the adoptium LTE stuff.