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Hello, i recently updated my macbook air 2018 to Big Sur but today I decided to downgrade it back to Catalina. After watching some Youtube videos and reading some articles I successfully created the bootable disk drive (I downloaded Catalina from the app store and then did the rest from the terminal). After that I went erased my Macintosh - Data from the disk utilities and continued to choose install Catalina. So, the process starts with a spinning globe, asking me for my wifi password and proceeds to install. The problem is that when the bar fully loads a warning sign appears on top of the globe and it says: “apple.com/support. -1008F”. I googled the issue but neither cmd+R, option+cmd+R nor Shift+opt+cmd+R work, since despite what i press and hold it automatically loads the same screen: the spinning globe asking for wifi password. The only thing I can do, is hold Options on the start up, but the pnly option given to me is to install Catalina and I can no longer see “macintosh” option anywhere. And again, after selecting install Catalina, the same process goes on until it loads only to show the same error. Can anyone help me?
Sadly since High Sierra one can’t easily back off versions. You see once your drive is converted to APFS Apple now sets a version ID of the running OS, the older installer won’t install on a newer version OS with a newer version of APFS. The only way to get around this is to completely erase the drive and setup a new GUID partition and install a fresh copy of the OS you want (what the system requires). I have not played with Big Sur yet so I’m not sure what else you can encounter as the systems firmware likely got updated too! The best way to do this is not depend on the WiFi connection. Instead get a USB-C SSD drive which you setup as a OS installer following this guide: How to create a bootable macOS Catalina installer drive Using the OS installer file link from here in Step 4 How to upgrade to macOS Catalina
