As long as using a VPN is not a problem for Duelbits, I don't think it's a problem either, but you really have to ask their service support if you can use a VPN and provide reasonable reasons why you use a VPN. Indeed, some people always want to appear anonymous, so they don't want to reveal their original IP. whereas in my opinion it looks like a child, but as long as it makes him comfortable there is no problem with me.
It's also important to confirm that Duelbits doesn't ban VPN use if that's not a problem I think using a paid VPN is the solution because it guarantees more security than using a free VPN because I've used it and it sucks having to share with other people and it's hard to access the site in the end That.
I have been playing here with VPN for years now, and I haven't had any troubles about it at all. I think that people who have problems do not have it because they are using VPN, they have it because they do not follow the rules and do something different.
I understand that it may not be that great for some people to see that they have lost the access to their accounts but if you want to avoid that then you need to make sure that you follow all the rules properly without ever going out of it. Many people do too many crazy stuff, like for example there are people with dozens of accounts, how could we expect them to stay? At that point using VPN wasn't the reason why they were blocked. That's why if you want to use VPN, make sure you follow the rules.