Same is happening to me “An error occurred preparing the update. Failed to personalize the software update. please try again.” on my M1 MacBook Air, i reset it to clear my SSD and near the end of the download for macOS Bigsur, that message just pops up. I’ve seen solutions on youtube that you can try, by the youtuber Mr. Macintosh, he has some good content for this type of problems and multiple solutions on how to fix it

After 2 months of having a bricked M1 Macbook Air I have to say that the only way to fix it if every other method has failed, is taking it to an apple store and booking an appointment with the genius bar. Or if you have a secondary mac at home, you can try downloading an ipsw file that apple provided to fix this issue and use apple configurator 2. I haven’t been able to fix mine because All apple stores in California are closed, this whole situation is bullshit ngl lol, I should’ve just built a pc instead.