>Restarting does not help.
Did you also try to reset the printing system as described in Reset the printing system on your Mac to solve a problem – Apple Support (UK)?
>Wireless function went down some years ago. Not tried USB yet.
So, Ethernet has been the only interface used? Directly, or via one of the LAN ports of a Wi-Fi router? It may be worth testing USB as well after resetting the printing system (and with a fresh download of the macOS 10.15 Catalina printer driver 1.5.0 from Brother).
However, if nothing else works, I agree with John Galt, it is time for a new printer. Unfortunately, AirPrint print servers are rather expensive, but you may be able to find a second-hand device via an online auction site. Despite being for AirPrint, it may not be a bad idea to double-check whether such a print server has any extra requirements or compatibility limitations.