My experience with smart devices:
- Generally all bottom of the barrel tech, I can't wait for matter and thread to proliferate and remove dependencies on some hacked together apps
- Usually the iOS app does pairing better than Android, but it's very device dependent. For instance having a device that's not running the latest Android or iOS is more likely to work then a new version. Effectively you want the version some hack project would've used when being hacked together.
- They tend to not like mesh wifi. I don't know why, but I'm guessing it has to do with the nodes not propagating / broadcasting discovery signals (particularly UDP). Sometimes it helps to unplug the mesh node(s) to force the initial setup to the main node.
- Dual networks never work. Better to just split 2.4ghz to its own said and connect all smart stuff to it
- Any complex network stuff is going to fail.
I'd split the networks, unplug your other routers, and try more devices. Especially ones running an older version of the operating systems.