If it helps, this is what I do to get the driver's work (Sorry for the "sof for dummies" instructions, but I document everything I do and once it works I stick with it. I don't have enough knowledge to optimize).
Nov 10 2021
Nov 7 2021
Just a follow up.
I thought I would post this here given that the other issues are closed.
Apr 21 2020
MFC-J6720DW works as a network printer, but I had no success setting this up directly connected via USB. To be honest I've never set up this printer using USB on any distro or Windows, so I'll leave it up to someone else to more exhaustively test this.
Apr 20 2020
The link to the MFC-J6720DW leads to the MFC-J5320DW file.