TweakTown reports that PS5 save files cannot be backed up via an external USB drive. This is unlike before on the PS4, where that is an option. Oddly enough, you can back up any previous gen game saves on the new gen console, which is especially strange. For example, you can still import and export a PS4 save file of Assassin’s Creed Valhalla to and from a PS5. This includes if you’re playing the game on the new console via backwards compatibility. But if you play the the PS5 version, then that save file can only be backed up via PS Plus.
And to make things even more confusing, the PS5 separates save files by console generation. This can lead to confusion when trying to load save files, and sometimes cause them to disappear entirely. Add all this to reports of PS5 consoles with issues from buzzing to bricking, and it’s probably not too bad a thing that we in Malaysia are getting the console late. But if you’re among those that have successfully placed a pre-order, then it looks like a PS Plus subscription is a necessary insurance for your save files. (Source: TweakTown [1], [2])