I have the same issue and I still haven't found a solution

Hi, sorry I don't was use the Settings -> App Store -> Account Sandbox but I just was use the principal iCloud account. In any case even if I use the main account and the OS recognizes that is a test account this should not prevent me from authenticating with other test accounts. However now that I have blocked the maximum number of main accounts if I want to transfer this phone to a friend or one of my family, or sell it, what can I do to solve it ? thanks Danilo

Same for me, these who make xcode have become very careless in these two years.

Removed unsupported VPN software, such as GlobalProtection VPN, and reinstalled it this fixed the Wi-Fi issues for me.