Also this one:

iPhones loosing wifi connection on Ubiquiti gear

https://discussions.apple.com/thread/254910871?sortBy=best

wifi not working after iOS 17.1.2 update

Source: wifi not working after 17.1.2 update – Apple Community

What solved it for me on two different iPhone models was to:

Turn off the **Limit IP Address Tracking** switch by swiping it to the left.

(Disabling this feature will allow your IP address to be visible again for that specific Wi-Fi network. Keep in mind that this change affects only Safari and Mail, not other apps². )