The Aqara Hub M2 does not need to be in close proximity to sensors like those for doors or windows, but there are some considerations for its placement:

- The Hub M2 supports Zigbee 3.0, which allows it to connect up to 128 devices, but it may require Zigbee repeaters to extend the range and ensure stable connections, especially if the sensors are far away or in different rooms or floors.
- For optimal performance, it is recommended to place the hub in a central location to minimize the need for repeaters and ensure reliable connectivity.
- If you plan to install the hub in the basement (Keller), make sure it is within range of your sensors and other devices, or use Zigbee repeaters (such as Aqara smart plugs or wall switches) to extend the coverage area.

In summary, while the hub does not need to be right next to the sensors, a central location with potential use of repeaters can ensure better connectivity and stability.