Can I add LNK2 to an ESP-Modular?

No. There is no LNK accessory port on ESP-Modular / ESP-M. Replace the controller with ESP-ME3 (or a fixed TM2 / RC2 if the station count is small and will not grow).

Do Modular station modules work in ME3?

No. Use ESP-SM3 or ESP-SM6 made for ESP-ME3.

When is TM2 or RC2 a better swap than ME3?

RC2 if the job is eight zones or fewer and you want Wi-Fi in one SKU. ESP-TM2 if station count is fixed at 4/6/8/12 and you do not need flow. ME3 if they will add valves or you want FG100.

Replace an ESP-Modular with ESP-ME3

There is no LNK2 upgrade for ESP-Modular or ESP-M. The current in-stock replacement is Rain Bird ESP-ME3: four stations in the box, hot-swap modules to 22, LNK2-ready, and the only residential/light-commercial Rain Bird clock on this shop that takes FG100 flow. Add LNK2WIFI for the free Rain Bird app. Keep the existing Rain Bird valves and heads.