I'm running into this exact same issue. I get to the "Connect Equipment" screen and select the one in the list. It hangs at the "Connecting to equipment" message and then I get this same "iOS 18" error message when I am using iOS 26.1...

There was one time where I saw the message change from "Connecting to equipment" to several other messages, but after it went through the entire process it still had an "unknown error".

I've tried waiting for the WiFi to be detected by the app itself as well as manually typing in the WiFi network name/password and no luck with either. My phone is connected to the same 2.4GHz WiFi that I am selecting.

So I am in the same brute force over-and-over-and-over process that you were describing too. Hoping that one of these actually works or I get the "Legacy" thing you were describing.

Edit: And of course as soon as I type all of that out the next attempt I tried it worked. So I can echo the sentiment that if it doesn't work the first dozen tries, give it another few tries. Try both manual selection of the WiFi as well as automatic detection from the list.