Installed Public Beta 4 (17A330h) yesterday, today realized backups to an older Mac ('11 mini) running Sierra no longer works. It worked fine on PB3, but now it keeps telling me the disk doesn't support the necessary capabilities. Is there an update to AFP in PB4, or something similar? Wondering if I should pull the trigger on upgrading my Mini to 10.13 (and if that would fix the TM issue) but that one is slightly more critical to household harmony than my laptop (which I only need for my livelihood so ¯\_(ツ)_/¯).