Two friends had this problem recently and both turned out to be broken VPN apps. Neither could remember why they installed them in the first place. And neither even thought that those apps could have been a possible cause. Interestingly, neither could be disabled using the VPN switch in the Apple Settings app. The simple solution was to delete the actual app from the phone. The two offending apps were Surfshark and Phone Guardian. Could these apps be vectors for malware? One of them reported that access stopped after accepting a suspicious invitation to follow an account on Instagram.
