My cellular data on iPhone 7 Plus, with iOS 14.3, works perfectly fine when I removed VPN.
I have an iPhone 7 Plus and I had the same issue as everyone else. When I first updated to iOS 14, I lost all data and could only call and receive texts. Only with WiFi could I open up my apps. The only thing that worked was when I removed VPN on my phone and then I was able to have data.