I'm setting up a PayPal Donate button with a personal account. I cannot find a way to setup Payment Data Transfer for Return URL with the PayPal Donate button. It worked a year ago (2018), but it seems to have been discontinued.
I believe that there was some talk of the discontinuation of PayPal's PDT. Whether or not that has happened, I believe that the general consensus is that you should likely switch your button notifications to the Instant Payment Notification (IPN) system. There are several reasons for this:
PDT has some major disadvantages, as discussed in this PayPal doc
The same link discusses how IPN resolves these disadvantages.
The fact that the IPN sends notification for all of your payer/payee interactions allows you and your business to provide the very basic due diligence. While there is some level of "opinion" involved, many people would consider this non-negotiable.