Cannot install apps via macOS Big Sur App Store
Okay, I found the solution. I found an Apple Developer forum (that I had to access via Google cache for some reason) that discussed related issues.
To re-iterate here:

Sign out of Mac App Store

Store &gt; Sign Out



Navigate to ~/Library/Caches in Finder

Keyboard Shortcut Cmd+Shift+G (Go to Folder)
Enter ~/Library/Caches

Click &quot;Go&quot;


Find the following folders in the Finder window and move them to the trash

com.apple.appstore
com.apple.appstoreagent


Reboot

 &gt; Restart...


Launch Mac App Store &amp; Sign in


Testing App Store downloads/installs after the above steps seems to have resolved the issues.