Are Big Sur setup files lost after installing?
Solution 1:
I can't say for certain with Big Sur, having never run it from scratch or indeed as an upgrade, but traditionally the app is stored in Applications, as "Install macOS [name]" & is deleted on successful run.
It doesn't delete it if you install to a different drive than the one the computer is currently booted from.
Otherwise, the trick has always been to duplicate it elsewhere before you run it. I keep a collection on an external drive… though I can't say I've ever been considered 'normal' in that respect :P
