Is it possible to have, assigning groups or ownership, something like
ln -s original link
where the original folder will be updated, all link folders will receive the new files, but any change to the files will not be in the original. The user will have write permission to the folder, but not to the files.
A symbolic link is just a redirection sign telling the directory traversal code “look there instead”. Once you get to the location of the files, it doesn't matter how you got there, it's the same files.
What you describe is exactly one of the common use cases for union mounts. See also Union mount on Linux although as I write it doesn't have the comprehensive answer that I'd hoped for. The basic principle of a union mount of override over original mounted at link is that link/file is override/file if it exists and original/file otherwise.
On Linux you can make a union mount with the overlay filesystem. Something like this (untested):
mkdir override work
chgrp users override; chmod g+rwxs override
mount -t overlay overlay -o lowerdir=link,upperdir=override,workdir=work link
On Linux and Solaris you can also use a "reflink" to the original file. A "reflink" is a copy of a file where only the metadata is initially copied. Any changes to the copy do not propagate back to the original file. Likewise, any changes to the original file are not reflected in the copy. Reflinks require the underlying filesystem to support copy-on-write semantics.
Reflinks are supported on Linux by the BTRFS and XFS filesystems (XFS requires kernel version 4.8 or later). Reflinks can be created on Linux using the cp --reflink... command or the ioctl( ..., FI_CLONE, ...) or ioctl( ..., FI_CLONERANGE, ...) functions.
Solaris 11.4 supports reflinks on ZFS, where reflinks can be created with the cp -z ... command or the reflink() function.
/tmpare protected from removal by other users... – Andrew Henle Oct 17 '19 at 23:06