Unfortunately this issue is not Whonix-specific:
Even if you manage to successfully configure a VPN within Qubes-Whonix, your VPN may still be detected and blocked:
The VPN may work If the IP address range is provisioned from a residential ISP. The Tor Project team has also acknowledged geo-blocking issues in the past:
However, ephemeral exit bridges for Tor (EEBT) and exit bridge Onion Services (HebTor) do not seem to be a significant priority at this point in time.