Alexa is a virtual assistance developed by Amazon. It's capable of recognizing voice commands so you can interact with Alexa and have access to their powerful actions using Skills.

How can I connect Sonoff devices to Alexa

At Yeti we decided to add Tasmota devices as a supported brand. It's true that we still have a lot of work to do in order to improve the integration but, right now, it's useful for many users (That's what they reported) See how to integrate Tasmota devices with Yeti

Recently, we released a premium version of Yeti This premium version open users to use Alexa capabilities to run charms they created in the app and then command Sonoff Tasmota devices.

Here you have the complete guide to connect Yeti and Amazon Alexa

Although Tasmota is an open-source firmware, at Yeti we weren't able to distribute the capability to connect Yeti with alexa, neither routine or charms features, due to the servers cost for us. This is why we request users to get Yeti premium to enjoy these features.