I just bought a home and in my apartment i just used philips hue to control my lights
In my new home i was looking in to using home assistant with a raspberrypi and a zigbee dongle for zigbee2mqtt but do i need 2 raspberrypi or can i install home assistant and zigbee2mqtt on one raspberrypi
The short version is yes you can
One device is fine - your easiest path is one device with HAOS on it - Z2MQTT can be installed as a HAOS Add-On. Iād just suggest you put and SSD and a small powered USB2 hub for your zigbee coordinator on that Pi for your sanity and stability - but otherwise - have at it.