An error occurred while installing the selected updates.

if i saw what exactly the error said, it would help me with my response. but going by your description, it would seem to me that you used wi-fi to download the upgrade. when downloading updates/upgrades, it's beneficial to use a wired ethernet connection. this is especially important for the big sur upgrade. the big sur installer is WAY BIGGER than previous upgrades. there is a lot of data being transferred, and it can become corrupted over wi-fi. if that is the case, i would delete the current big sur installer from the applications folder, empty the trash, then connect the mac to the router with a wired ethernet connection and restart the upgrade from scratch.

Are you downloading and installing from the System/Software Update preference pane?

If you are go to the App Store, search for Big Sur and download and install from there.

How much free space do you have on your boot drive. Upgrading from older systems require a minimum of about 50 GB of free space.

The check if MDM is installed >> Apple Icon >> About this Mac ?? System Report and scroll down on left looking for Profiles. Anything appearing there - If Yes, Corporate SA is . . . arrive at own conclusion.

Please clarify " I keep getting this when attempting to update to Big Sur "

An update involves updating within the same version of macOS ie 10.15.7 to 10.15.7 Supplemental.

An upGrade is moving from Catalina 10.15.7 Supplemental to Big Sur 11.2.1.

Thus different methods and processing are involved requiring different types of assistance to help resolve the situation.

Has one read all the details regarding upgrading to Big Sur especially the section about the Empty Space Requirements for a successful installation ?

That’s not the problem. I’m on Ethernet, and I’ve deleted and redownloaded multiple times. I’ve tried directly from Apple as well as via software update.

sorry you already tried that and it didn't work, but my answer was directed to the OP.

Many thanks for that advice - I didn’t know you could see that, and that’s very helpful for future reference. In this case, it shows no profile, so maybe he was telling the truth...

MacBook Pro(13-inch, 2017, Four Thunderbolt 3 Ports) It is constantly giving "unexpected error occurred while installing" the upgrade from macOS Mojava v.10.14.6 to macOS Biog Sur 11.2.3 - 12.21GB

Sorry. Replied unintentionally.

I have a similar problem, and I've tried all the "typical" solutions. My 16" MacBook Pro 2019 is unable to install Big Sur. Interestingly, I also cannot install the most recent supplemental update for Catalina (I'm running 10.15.7 build 19H15, but the most recent Supplemental Update (build 19H524) will not install - I get the same error message as Corning). I have plenty of memory available. I've tried booting in safe mode, resetting PVRAM and SMC, and even reinstalling MacOS via recovery mode - nothing works. I use this computer for work, although my corporate SA swears there's no MDM issue at play here.