See the following note in the macOS 11 beta release notes

New in macOS Big Sur 11 beta, the system ships with a built-in dynamic linker cache of all system-provided libraries. As part of this change, copies of dynamic libraries are no longer present on the filesystem. Code that attempts to check for dynamic library presence by looking for a file at a path or enumerating a directory will fail. Instead, check for library presence by attempting to dlopen() the path, which will correctly check for the library in the cache. (62986286)

Thus loading frameworks using Native.loadLibrary("Foundation") no longer works because the code has checks using java.io.File.exists to locate the framework.