I've focused on IoT-devices that uses the ZigBee-protocol, which can be integrated directly (trough a ZigBee controller of your choice, like deConz) into HA without the need of any proprietary hubs. Luckily IKEAs IoT-devices (primarily lights, controllers and switches) use the ZigBee-protocol and are decently priced. I have also used cheap environmental sensors[0] from China that supports ZigBee. I really like the idea of only using components with an open protocol and being able to isolate my IoT-setup to my local network. Everything would still work if I lost my internet connection and no data is leaving my house.

[0]: https://www.aliexpress.com/item/4000713849766.html