Look into ZWave and ZigBee mesh networks. I run Home Assistant with a couple hundred devices and integrations. ZWave tends to be my hardwired switches, and ZigBee tends to be my battery operated motion sensors, remotes, etc.
Personally, I run Home Assistant on its native HAOS on a raspberry Pi. In addition to Home Assistant, I have lots of automations running in Node Red, a no/low code orchestration addon.
For voice control, I’m playing with the Atom Echo.
Part hobby, part time and energy savings. One thing I love about Home Assistant is the integrations with so many devices and services. I have smart switches., remotes, smart plugs, energy monitors, RGB bulbs, thermometers, etc.
It’s a slippery slope of wanting to integrate absolutely everything! My doorbell, alarm system, thermostats, garage door, door locks, and so on.
Many are local “smart devices” using ZWave and ZigBee, and others are cloud integrations with other services.
I’ve gotten to a point where the Home Automation routines I rely on are so useful that I get annoyed if I ever have to do things “manually”.
Couple examples:
I have a remote by my bed that, when the goodnight button is pressed, turns off all the lights, sets the HVAC back to programmed mode, puts our computers to sleep, arms the alarm, locks the doors, and closes curtains.
I have a button by my garage door that sets an “auto arm” toggle that opens the garage door, unlocks the door to the garage and the waits for me to close the garage, at which point it arms the alarm, turns off the lights, locks my computers, turns off the HVAC, closes curtains, locks doors, etc.