Package with native library

Hi,

I’m trying to create a custom unity package with a native libraries. My package structure is like this (here mylib.so is libassimp.so)

My package
package.json
Runtime
myasmdef.asmdef
Scripts
mycode.cs
Plugins
MyPlugin
myplugindll.dll
myplugincode.cs
Native
linux
x86_64
mylib.so
osx

win

But as I import this package into another Unity project, it complains in runtime as

Error loading unmanaged library from path: libassimp.so
libassimp.so: cannot open shared object file: No such file or directory

Could you give any help?

Do you have .meta files for all the plugins?