So I’ve sold my MacBook Pro as I never use it. (Long and short, I love my iPhone and my iPad. I can’t get on board with the MacBook Pro. I’m a Windows guy, yes, I’m an antique...)

When you wipe and reinstall, it doesn’t give an option. It just slaps Mojave on there.

I wiped the drive and reinstalled the OS. It installed Mojave. I created a user, installed BigSur. Now I want to keep BigSur installed but I want to get the stupid computer back to the point that it is asking for you to “choose a region”, “choose a language”, “create user”, etc. is this possible?

You can either boot the recovery partition, which will let you reinstall the most recent version of macOS. Or, you can boot to Internet Recovery Mode, which will allow you to reinstall the macOS version that was factory-preloaded on your Mac at the time of purchase.

Recovery Mode: Hold down Command-R just after the startup chime until the Apple logo appears. If you get the login panel, you weren't quick enough.

Internet Recovery: Hold down Command-Option-R just after the startup chime until a globe logo appears. If you get the login panel, you weren't quick enough.

Since the Internet recovery loads everything over the 'net, having a good Internet connection speeds things up considerably. For example, you'll probably get better results over a cabled connection rather than WiFi.

Older versions of macOS are downloadable for the App Store. I will generally build an installation thumb drive for each major version release, and keep them around just in case, but I have relied on the Internet Recovery approach more than a few times.

Cool. Thank you. I will give the recovery mode a shot.

So recovery mode reinstalled the OS. I’m in the same spot I was in earlier. Guess the guy that’s buying it can either wipe and reinstall, or add a new user and delete the one I created to update to BugSur.