Hardware decisions (hub, thermostat, sensors etc.)

I’m new to the whole topic. I have a rough idea what i wand but no main plan which is the best and cheapest way to achieve. Generally i hope to find a way to buy products which do not require separate hubs.

  1. Thermostat which have to be cheap since i need maybe 6 of them.
    Is it possible to connect Max! 99017A0 thermostats without the MAX! Cube LAN Gateway?

  2. Xiaomi AQara Smart Temperature Humidity Sensor
    This sensor has zigBee, so i hope there is no problem to connect them.

  3. Ikea TRÅDFRI which i already have
    Since they have zigBee there should be no problem as well

I have an NVIDIA Shield and there is an USB-Dongle from Samsung SmartHub. The dongle supports ZigBee and Z-Wave maybe this is an good option. But it will be hard to get it to germany.

What you think? How can i get a cheap solution for the radiators? And how i connect the devices to my (not currently build) home-assistant?

Thanks a lot!
Ulli