Apple made the change, not Xerox, you don't look to Xerox for help when Apple caused the problem.
Apple provided FTP for free, then they took that away, at no part of that did Xerox make any decision and there is no reason for them to do so.
If you want to use FTP you have to get an FTP service, do not blame Xerox for that.
If you want SMB to work, assuming it is properly setup on the Mac, just update the firmware on the printer and use SMB. While it did not work in earlier software (Due to Apple using their proprietary AFP in SMB's place), Apple later went with the Standard SMB2.
So for the Mac, just Apple > System Preferences > Sharing
Add the folder, add the user with Read&Write , remember the IP (highlighted) then click Options
Make sure SMB is checked
Then set it up in the Address book
Those solutions all work just fine so you have to troubleshoot your method of implementing them.
I can't give you any magic fix, each has their own things that need to be done, like the App from the app store, as stated over and over in the thread comments, you need to create a folder within the root folder to make it work. And the port is 2121, which is listed in their Support site
I knew both solutions you indicated but I could not solve the problem.
FTP Server don't work, also with port 21.
Many of my work colleagues have decided to change the scanner.
I would like to continue using my Xerox, how can I do?
There are many 3rd party apps and methods to get FTP back.
Some are quick and simple paid apps
Not too long, not that hard and free
Here is an Apple support thread
Hello everyone, I have a Xerox 3615 and an Imac with hIgh Sierra.
Unfortunately High Sierra has removed ftP.
for this reason I cannot longer transfer onto my Imac scans via fTp.
SMB does not work.
How do I fix This problem?