Since this is a rather technical post, I’ll do it in English, increasing the chance of people being able to use it a lot.
Recently I bought a number of smart power plugs, sold via Amazon (.de) and produced by Avatar. Note that they sell 2 different types: the ones with and without power measurement. Strangely enough, at the moment the ones with power measurement are slightly cheaper even than the ones without power measurement. Just make sure you buy the ones you expect to buy (I didn’t and ended up with 8 plugs that don’t measure power, I’ll put them to good use, but would have rather have those also measure power consumption of the devices connected to them).
The plugs are being advertised as being controllable by Alexa, Google Home and IFTTT. That is nice, but I want Tasmota on them so that I can easily connect them via MQTT to Home Assistant (or any other home automation system that I choose to use) and so that I can make 100% sure that they don’t have to / cannot connect to the outside internet.
To do that I use the Tuya-convert tool to add the Tasmota firmware (note: warrenty voided once you do, if you follow these instructions, you’re on your own, I can’t help you if you brick your plug or if it doesn’t work, this is just a post describing how I got it to work) to the plug so I can control them from Home Assistant (and via the webserver on the plug provided by Tasmota). Because I needed to configure a total of 8 plugs, I also used decode-config to make it a bit easier (quicker) to do (although it probably took more time to figure out the tool for this first time than it would have to just do it by hand).