That folder tree was probably moved to "/Users/Shared/Relocated Items" as part of the migration process. A "Relocated Items" folder alias to that location should have been created on your Desktop during migration. A PDF in that folder explaining the contents resides inside that folder along with items that were relocated. The recloated items folder exists in part to the changes which came with macOS 10.15 Catalina with the introduction of a read-only root volume for the OS.There is a process you can use to restore that directory tree to the 10.15 root folder by creating a symbolic link in root directory using the synthetic command (see man synthetic.conf). For a better explaination and how to see Creating root-level directories and symbolic links on macOS Catalina

The solution by user "esaruoho" is correct except step 3 should be "csrutil disable" and step 12 should be "csrutil enable". I fortunately had made a clone of my Mojave boot disk 4 days before some update screwed up my MobileDevice framework. Fortunately I had not yet updated the clone version on that disk.

Your machine probably shipped with a "newer" variant of macOS Catalina due to newer hardware which Big Sur updater does not yet recognize. Wait until the Big Sur beta catches up.. probably in the next beta release.

Unfortunately the installers are protected by the System Integrity Protection (SIP ) system. To delete the installers boot your Mac into Recovery mode (CMD-R) and open the terminal application from the menubar and execute the following command to disable SIP. csrutil disable Restart your Mac. You should be able to delete the installers. After you delete the installers boot back into Recovery mode (CMD-R), open the terminal application again and execute the following command to re-enable SIP. csrutil enable Restart your Mac and enjoy.

You can enable it in the menubar control center.

You can enable it using the menubar control center.

Same upgrade from ßeta 4 to ßeta 5 issue here on a M1 Mac mini external TB SSD drive. Even trying to update the external TB SSD using the full ßeta 5 installer from my internal SSD ended in failure. I guess unless Apple releases an updated ßeta 5 installer we can only hope the issue is fixed in ßeta 6. I did submit a Feedback report.

Same here. Successfully updated from Beta 4 to Beta 6.

If you are using any network content filters like Little Snitch, LuLu, etc. this is a known issue. Disabling the content filter is the only solution to restore normal network connectivity at the moment until Apple resolves the issue.

Yes that warning is standard practice for HomeBrew during a macOS βeta. Shortly before or when Sonoma is released it will be supported.