I use the SONOFF ZB Dongle-E with Zigbee2mqtt, as do many others. As Rich said, if you have two floors then you’ll want some routing devices in-between.
If you’re interested in presence sensors, the Sonoff SNZB-06P works as a router. So do most smart plugs.
I actually wish that I’d gotten into Zigbee much sooner. Zigbee devices tend to be much less expensive than WiFi/Z-Wave alternatives and, in my case, more reliable. I’m particularly happy with IKEA’s newest sensors.
I’m a little confused by this. By definition, a basement is partially or completely below ground. In Canada (and I assume the US), the first floor is always completely above ground, so a basement would never be the first floor. Is that different where you live?