The AUR package installs OK but printer won’t print in duplex mode. Haven’t tried it on this install of endeavourOS but have tried before, and reviewed the whole issue with @joekamprad in the forum link I mailed before. Finally talked closely to a brother service agent and then we concluded that for some strange reason the AUR package was not working ok, but if I install by using the rpm provided by brother, using rpm-tools, everything worked OK in my last EndeavourOS i3wm install.
You can check this exact comment at the forum post for clarification: