Brother Printer Drivers for Models: HL-4570CDW & MFC-L2720DW compatible with iMac OS 10.13.6.

Hi,

You will find drivers here:

https://support.brother.com/g/b/downloadlist.aspx?c=us&lang=en&prod=hl4570cdw_all&os=10045

https://support.brother.com/g/b/downloadlist.aspx?c=us&lang=en&prod=mfcl2720dw_us_eu_as&os=10045

Also, the Brother MFC-L2720DW is listed in About AirPrint - Apple Support as a model supporting Apple's AirPrint technology. This means that this printer should work with macOS 10.13 High Sierra without additional drivers at all, provided that the printer and the Mac computer are connected to the same network (Wi-Fi router). AirPrint works with wireless (Wi-Fi) or wired (Ethernet) network connections, so you could choose to wire the printer by Ethernet cable to one of the LAN ports of the router (instead of a wireless printer connection). Ethernet may be more stable.

For a USB printer connection, drivers would be needed.

Reset the Mac printing system to solve a problem – Apple Support (UK)

Add a printer on Mac – Apple Support (UK)

That sounds like a question for Brother.