an error occurred while running scripts from the package “InstallAssistant.pkg”.

Hi there slessor161,

We understand you're experiencing an issue with installing macOS Big Sur, and we'd like to see how we can assist.

Get started with the steps here: How to upgrade to macOS Big Sur

If the issue persists, disconnect any peripheral devices, and attempt the install again.

Also, create a new user account, and try installing macOS Big Sur there: Set up users, guests, and groups on Mac

Cheers!

^^ By far the most unhelpful response I've seen by a "specialist." Makes no attempt to explain the root of the error and simply tells you to take some generic steps (which proved unhelpful) to solve what appears to be a specific problem. >:/