I see so many posts saying go to Tasmoto I thought I would come and ask who has given this a go?
Which devices can be flashed and what functionality is gained or lost?
Sure I also read you need to have a server running in the house as well, is that right?
It all sounds very involved, was it worth it for you?
I have Tasmota flashed on one of my sonoffs and you loose control via the app. You won't be able to have your sonoff connected to the eWelink app anymore, only locally via the device's webpage or together with another system like Domoticz.
Yes, you can use eWeLink any longer after flashing Tasmota. But you can use a local automation hub (Domoticz, openHAB, Home Assistant). You can also control it with the Amazon app and many other MQTT apps like Yeti or Yonomi. Many of these also still give you the ability to control the device remotely which away from home. Replacing the firmware just opens up a great deal more options and automation features.