RS-485 is a shared bus, so you need to use some kind of a protocol to arbitrate access, and to make sure you don't flash unintended devices.
BACnet is one example, but other protocols can work too.
BACnet is one example, but other protocols can work too.
You can already hook up an RS-485 transceiver to the UART ports and use it today with the UART driver. Esphome also has a Modbus controller component. What are you referring to by “generic” RS-485 that isn’t available already?