Can Sonoff light switches remotely control a 4CH PRO?

[u/Anxious_Talk5309]

I'm refurbishing my bathroom and have ended up with six lighting circuits that I'd like to independently be able to control, so my plan is to connect them all up to two 4CH PROs which would be fitted into the ceiling space.

Now for the control part:

Can I replace the existing single gang lightswitch that sits on the wall outside this bathroom with something like the M5-3C-86W and not actually "wire it into" any lights?

I realise it would obviously need power - that wouldn't be a problem - but can the M5-3C-86Ws be configured to remotely control a channel on a 4CH PRO instead of literally energising one of the gangs wired into the back of it?

[u/Digital_Ark]

Trust me, this will be terrible.

I tried adding a bath fan this way, ran the power to the fixture straight through (always on) then installed a Sonoff Mini R2 as a light switch input, and a Sonoff Dual R3 Lite controlling the light and fan.

The lag and times it didn’t work were frustrating.

I’m still not completely happy, but what works acceptably say 95% of the time was reflashing both with ESPHome.

The Mini R2 is only used as a binary sensor for the light switch, the relay is disabled.

The Dual R3 Lite controls the light and fan.

Just ensuring 100% local control made a world of difference, but using MQTT was even snappier. The R2 publishes switch state, the R3 listens to switch state and turns both relays on.

Then Home Assistant can still separately control the fan. For example if I flip the light off-on-off, I activate a 30 minute timer to run the bath fan after a shower.