AFS, the Andrew File System, has kernel support. [0]
AFP, the Apple Filing Protocol, is a network protocol, not a filesystem. It has several userspace implementations. [1]
AFS, the Apple File Service, is AFP plus other auxiliary protocols. [1]
APFS, the Apple File System used in modern MacOS, has read only support in userspace, and there is work on a read/write kernel module that is not mainlined. [2] [4]
HFS, the Hierarchical File System used in older MacOS, has mainline kernel support. [3]
[0] https://docs.kernel.org/filesystems/afs.html
[1] https://en.wikipedia.org/wiki/Apple_Filing_Protocol
[2] https://en.wikipedia.org/wiki/Apple_File_System
[3] https://www.kernel.org/doc/html/v5.8/filesystems/hfs.html