Honestly most smart home devices support HomeKit these days – lights (Philips Hue, IKEA), thermostats (Ecobee), locks (Yale, Schlage), blinds, cameras, sensors. And anything that doesn't can usually be bridged through Homebridge or Home Assistant. It adds up fast once you start – lights alone can be 50+ if you do every room.
Every device compatible with the Matter standard[1] can be used with Apple Home (and with every other solution that supports Matter, like Google and Amazon ones), so almost everything is compatible with everything out there.
148 Home Assistant (bridged) accessories checking in... sign me up for the beta!
On the accessory count, call it a 2-story house, ~5 rooms per floor, plus an outdoor zone:
2x thermostat, 2x speakers (HomePod), 2x door, garage door, 2 lamps per room, pool "accessories" (filter, cleaner, heater, lights), 2x outdoor lights... that's 27 just off the bat!
Now adding Home Assistant and you start getting 2x Zigbee interior door sensors (privacy locks/detection for when we have a babysitter), 2x interior motion sensors (upstairs/downstairs stairwell), patio string lights, front throw/spot lights, 3x decorator bulbs for the hanging entrance lamp (bridges three bulbs as one since they're individually controllable bulbs instead of a smart fixture or switch), an AirPlay compatible TV, fridge and freezer temp/humidity sensors, the outdoor AirPlay speaker, outdoor gate open/close sensors (front and back), outdoor motion sensor...
...and then the random other "every HomePod technically has an in-built temp and humidity sensor", the Home Assistant integration for the router that reads the packets in/out, the printer thing that reads the ink status for all the ink cartridges, etc.
It's a lot, but start with a single reading lamp and night light per room. Make a "lights" and "mood" scene per room/floor. A few key motion/door sensors (turn on a downstairs mood light when opening the door after sunset, turn on the hallway mood light when motion is detected after 9pm, etc).