@ksred @Geneman14 "...instructions on how to update, alongside a file named MonitorCustomerTool_V1_5(1).7z which extracts into a runnable program called RCDTool.exe. They explicitly said that it must be performed on Windows."
How did you connect the Win PC to the monitor - did the instructions require a specific method?
This is significant in determining the reason that Windows is necessary.
Older RealTek monitor boards need to transfer the firmware data over a DP to DP connection, using the DDC/CI protocol.
MacOS doesn't naturally support DDC/CI, and Windows does.
Maybe if a Mac can be made to support DDC/CI so the firmware update can be achieved using 'virtual Windows'?
Better Display is a good way to get MacOS to support DDC/CI, but I don't know if that can help prevent an update failure when no Windows PC support is available.
Because I do remember reading of people having success at running a .exe Windows updater on a Mac, but don't know how this was achieved.