Is there a community specific to FOSS or just general privacy oriented IoT? With plenty of hardware discussion along with software. Routers, piholes, Meshtastic, anything IoT but open source. If it touches a network but you want it to do something it doesn’t. Flashing a doorbell camera with FOSS firmware. Hosting media servers on your phones Hotspot. Loading gcode to a printer from anywhere. There are so many things and possibilities.
If there isn’t someone should start one, OpenIoT or something catchy and relevant.
Check the link I posted above, or you can look at the 802.15.4 wiki for an overview.
https://en.m.wikipedia.org/wiki/IEEE_802.15.4, scroll to the security section.