This seems to be similar to issues others are having after the Safari 14.1 update 4/27/2021 that was part of the Catalina 10.15.7 update and it relates to JavaScript.
Test the following:
Turn off “Enable Javascript” in Safari: Preferences: Security
See if this resolves the the issue loading pages
This is not a solution since pages are only partially complete and lacks any Javascript functionality.
I am still searching for a fix.
Bottom Line: At this point this is most likely an Apple bug/issue related to 14.1 and they need to offer a fix other than an OSX reinstall and that reminds me of the #1 Microsoft Windows issue solution!