You should always ask in livechat to see if a casino is VPN friendly. Personally, I have the impression that more and more casinos don't mind the use of a VPN, I know some bigger casinos don't like it but I know of multiple casinos where I can use a VPN without any problem.
There is no need to contact customer support for this, actually, as it’s clearly stated on their home page that:"Niyvi.com – No KYC Withdrawals,
VPN Friendly & Exclusive Bonuses!"
I doubt their live support would tell you otherwise.
They are a kyc-free and they are planning to create/become a completely decentralized casino, so don’t see why they would prohibit the use of VPNs or any other tool that enhances users’ privacy!