A Raspberry Pi runs <a href="https://homegear.eu" target="_blank" rel="noopener">Homegear</a> and <a href="https://github.com/hobbyquaker/homekit2mqtt" target="_blank" rel="noopener">homekit2mqtt</a>. It is equipped with two 866MHz radios for Homematic and MAX!.
Additionally an MQTT broker and the homegrown control software (<a href="https://gitlab.com/wolutator/dispatcher_ng" target="_blank" rel="noopener">https://gitlab.com/wolutator/dispatcher_ng</a>), which communicates with Homegear, homekit2mqtt, the MQTT433MHz bridge (see below) and other homegrown web clients via MQTT, resists on it.
There is also a DIY MQTT to 433MHz bridge to control Intertechno and other 433MHz plugs (<a href="https://gitlab.com/wolutator/Mqtt433Gateway" target="_blank" rel="noopener">https://gitlab.com/wolutator/Mqtt433Gateway</a>).