Re: Let this be a lesson
"for anyone even daring to think about using IoT for this sort of thing."
Depends on how you do your IoT. I am spending months deploying IoT at home, each step building on the last and tested. My "hub" is Home Assistant running on a Lenovo Thinkcentre (which is properly designed to live in harsh environments). It is backed up and is on a UPS and ethernet connected. I also have a standby VM, just in case. https with a Lets Encrypt cert. and HA Proxy on the front (pfSense router). I have multiple VLANs, host firewalls deployed etc. I maintain my home network to as near to PCI DSS as is possible (yes, really! I'm CREST accredited and do ISO 9001 and 27001 at work) One other design requirement is that everything fails safe and/or has a manual control where applicable.
This lot has to be signed off by wifey ...