Similar to user_cache_dir but system-wide. Looks like on *NIX it should be /var/cache if following FHS. Windows is not that clear though, CSIDL_COMMON_APPDATA seems appropriate but it is already used for site_data_dir and CSIDL_LOCAL_APPDATA is used for user_data_dir. Maybe people more familiar with windows could suggest something. I'm happy to contribute the implementation myself.

PS: thank you for keeping appdirs alive 🙏