One of my broadlink two gang switches malfunction recently, just less than 1 year of use, one of the gang always on.

Quality of those China electronic products still have long way to improve, especially those without big brand.

All z-wave products (around 8 devices) I bought from US is still working fine, without a single failure, quality always come with price, China brand so far only Xiaomi products are more reliable, I have tried Kudled, Broadlink, and some other non brand, all failed within a year.

I only use sonoff switch less than 6 months, still observing, but I looked at their PCB quality, I doubt it can last long.

one Sonoff will do, just make sure you put the Sonoff in the main cable before it splits to the other 4 lights
Turn off your mains breaker before working on it.

Is there like tutorial/video on how to properly connect the capacitor?
Sonoff T1/YJZK- WIFI & RF switch : Reliable and still working fine, but need to add neutral wire for installation
Broadlink TC2 - Seems like there's always complains about this stopped working in a short time or other issues
Chuguan - This one RF only, I only bought one to test it out and so far so good, same price with sonoff t1 though
Xiaomi Aqara - Only up to 2 gang only, needs gateway for pairing, no need neutral wire

Any switch with L and N wire would be reliable like Sonoff

On the electrical outlet yeah, not for switches
So need to add later

Only 3 in socket have Neutral wire. Switches does not have one. If you see many wires it is just because the L wire is looped in the switch + the wire to the bulb (Yellow one in the diagram previously)

Depends on the electrician
In kuantan, this wireman charged for rm15 per outlet to add neutral wire

If you got aircond/water heater switch there will be neutral there.. But if light only don't have.

I mean you can take the Neutral from the aircond switch. My home all room got aircond switch beside light.. Bathroom got water heater switch.. Only living and kitchen got light only..

Another option is to use sonoff module installed near the light. Got RF and WiFi type. This way no modification needed. The switch on the wall is normal switch but need to switch on all the time. The module on the ceiling will act like a remote switch

Install something like this on ceiling

Bro, you've tried the philips smart led bulb? How's the brightness?
Pretty much same price in taobao, should be ok

Plaster ceiling will not block signal but no access. Can just camouflage it in decoration or if you have down light, can place it somewhere near

Yes i used 2 Xiaomi philips. Brighness ok 5700k

Spec
Xiaomi Philips Smart LED Ball Lamp  -  WHITE 214950401
6.5W E27 220 - 240V 450LM 3000 - 5700K Stepless Dimming APP Control
Bought here https://www.gearbest.com/smart-lighting/pp_...095.html?wid=21

Here more cheaper https://shopee.com.my/Xiaomi-PHILIPS-LED-Sm...TxoCI2oQAvD_BwE

Semua boleh....