I'm currently testing how to let users install Big Sur via VPP (and made available in Self Service), with the catch being that the users are not admins. Right now, it prompts the user to enter admin credentials which won't work and I've tried deploying the Big Sur stub installer as a package and then running that in the background but it doesn't work that way either. Can this be done or do I need to get the installer on the machine some other way and then write a script to run it interactively but with elevated permissions?
I have a policy that copies the Big Sur installer to the Applications folder, and then a second Self Service policy so that the user can install at their convenience. This document is more geared toward doing an erase install of macOS, but is helpful as far as going over how to use the startosinstall process: https://www.jamf.com/blog/reinstall-a-clean-macos-with-one-button/