that two DHCP servers on the same network is … difficult
I think that's a little harsh - especially when the advice is to run the IoT *on a different network*. Thus neatly avoiding the problem of two DHCP servers on the same network..
 Which isn't actually a problem at all if you want them to be serving the same ranges - my home DHCP setup has two DHCP servers, each serving half the scope. One is configured to delay more than the other so the quicker responding one is almost always going to respond. And, since I do have a second network for guests and IdiocyOfThings devices, the DHCP servers all have another virtual netword card on that separate network, both serving half the range on that network in the same way as they do my live network. And the IoT network has *no* access to my live network since my firewall also has a virtual adaptor on that network and rules to prevent traffic from leaking across.. (and allowing DNS access to the IoT network and the DNS used won't resolve any internal addresses on my other internal network ranges). Slightly OTT for a home setup but I had some fun building it..