I now have two machines, a MacStudio (M1max processor) and a MacPro (Intel processor). The contents of $HOME/Documents got lost on the MacPro. I also have a laptop (MacbookPro, macOS Monterey) which I won't discuss.
Previously on macOS HighSierra on my MacPro (and earlier):
Dropbox Folder: $HOME/Dropbox
Documents folder with contents: $HOME/Dropbox/Documents
Symbolic link: sudo rm -fr $HOME/Documents; ln -s $HOME/Dropbox/Documents $HOME
Dropbox backup folders: (NONE)
This worked fine for many years, syncing correctly with my laptop; some macOS updates required me to re-link the Documents folder.
I purchased a new MacStudio (with the Apple M1max processor). That forced an OS upgrade to macOS Monterey.
Now on macOS Monterey on my MacStudio:
DropboxFolder: $HOME/Library/CloudStorage/Dropbox
Documents folder with contents: $HOME/Documents
On my MacStudio I manually moved $HOME/Library/CloudStorage/Dropbox/Documents/* to $HOME/Documents
and deleted $HOME/Library/CloudStorage/Dropbox/Documents. So $HOME/Documents is correct, with contents.
Dropbox backup folders: Documents, Desktop
Note that I cannot remove $HOME/Documents and link it into the Dropbox folder -- the OS won't let me (via either the Finder or Terminal/bash).
Now on macOS Monterey on my Mac Pro:
Dropbox Folder: $HOME/Dropbox
Documents folder with contents: *** NOWHERE ***
Dropbox backup folders: Documents, Desktop
There is a "magic" symbolic link from $HOME/Documents to $HOME/Dropbox/Mac\ (2)/Documents -- the Finder cannot see it but Terminal/bash can. It is empty.
Note this is the OLD organization, so it's no wonder that $HOME/Dropbox/Documents is missing. It appears to be setup to backup Documents, but that is separate from my MacStudio -- it did NOT sync to the backup from my MacStudio, but rather created a separate backup.
How do I get my $HOME/Documents folder AND ITS CONTENTS to be visible on both machines, and to sync between them?
Google finds lots of OUTDATED instructions; I need to do this NOW (February 4, 2023).
(Fortunately I have TimeMachine backups.)