Hello, I had the same problem (iPhone 13 pro max), shows connected in the settings but no wifi icon or connection whatsoever. I used data for half a day but when I got I really was a problem because I have no data in my appartement. Anyway, I tried nearly everything like resetting the connections to default and stuff but in my case the real problem was PROTON VPN (I really like this vpn tho) my explanation is that the vpn is constantly working in the background, even if you close it with the swipe up thingy, and when it is compromised, it block any wifi connection. The exact moment when I got this problem was when was in on a slow public museum Wifi and I tried to connect proton vpn, it didn’t managed to connect to us server at first and I tried a second time but it got stuck trying to connect, I didn’t pay attention and close the app but it was running in the background even after restarting my phone so I deleted proton vpn and my WiFi came back instantly.
If it is not the problem try a factory reset and if it also doesn’t work I guess there is a problem with your motherboard..
sorry for the long comment and poor English
May you find your answer!