~snip~
It depends on the VPN service you have used, how can the casino distinguish between IP address with and without VPN? of course it's because how far the change of your IP address. This day the VPN service use Germany location, tomorrow the VPN service use France location, the next two days the VPN service use Japan location, this is clear a red flag in your account.
But if you use a premium VPN service where you're allowed to choose which country and which city you want to connect, it make the casino wouldn't know if you're use VPN.
Well, there are some ways to guess that the user is using a VPN service, because most VPN services that are available to the public only have a set of IPs available to them, so once they figure out one IP is a VPN, then any future users of that VPN getting that IP will be "discovered"
Well, for some casinos, this is probably hard for them to figure out, most especially if the casino is pretty new and coming up, the only ways they are able to figure out a user is or has been using VPN is when the ask such user to pass kyc verification, and discover that the location their system has recorded for the user through his or her IP address is not the same location in the document the user provided.
Another way again is that if the user is not consistent in making VPN, or makes use of different VPN services for different sessions on the casino, this will be linking the user to different IPs which in turn will make the casino want to investigate the reason for the different IPs, from this investigation, they will find out that such a user is making use of VPN to access their platform..
Yet another way, and this i believe to be the most simplest way, is by the casino installing a VPN dictator, this piece of tech and easily detect when a user is accessing the casino through VPN and immediately report to the casino.