Requires a connector with RS485: W32 with an RS485 module or LilyGO T-Connect (module in slot 1).
Connect A to A (D+), B to B (D−) and ground; use twisted pair, with a 120 Ω resistor at both ends of a long bus.
In the panel, set baud rate and parity matching the device (e.g. Eastron SDM120: 2400, SDM630 and Growatt: 9600, usually 8N1) and the device's Modbus address.
Each device on a single bus must have a different address.

RS485 works without Wi-Fi too — readings are queued on the connector and sent once connectivity returns.