Not really relevant to this thread, but I have an older Brother Multi-function printer, scanner, copier, fax machine that is no longer supported by Brother in the current macOS. There are printer drivers that still work fine, but their older scanner software won't run under current macOS and their current scanner software no longer recognizes this older device.
It does have a built-in feature that can scan and upload a PDF to an FTP server, you can configure the FTP server user/account info on the printer admin page via a web browser. At one time, I knew how to configure the ftp server on the Mac in OS X, but with periodic updates, you might have to set it up again. I found an app called "FTP server" that lets you set one up on the Mac. So, using the Brother built-in scan to FTP server feature, and setting up the FTP Server app on my Mac, I can still use that old scanner part of the multi-function device. It is handy because it has a multi-sheet feeder as well as a flat top scanning bed.