People talk a lot about home-assistant but there is another part to that setup; the devices themselves and the firmware they run.
If you stick to ESP8266 devices mostly you can use things like Tasmota and ESPHome. Zigbee/Z-wave is good I've heard but nothing compares to the interoperability of good 'ol WiFi.
It costs like less than $15 for a Sonoff Basic R2, another $5 for a knock off FTDI USB programmer. With a tiny bit of soldering you can put some programming pins on the Sonoff and flash Tasmota. From there you can use Mosquitto to control it, or the HTTP API, both open and interoperable protocols.