Can you reproduce this? --I tested a bunch of VPN providers and found several that do not work. Below I give some examples. I include the provider name, providers VPN config profile name, and testing results on two different GLi firmwares. (3.005 & 3.013)

VPNgate 175673389

3.005: TCP works
3.013: successful VPN connection terminates browser access / cannot ping router *

CryptoFree ed255519

3.005: failed to connect
3.013: failed to connect

CryptoFree ed448

3.005: failed to connect
3.013: endless connection cycles

Cryptofree secp521r1

3.005: works
3.013: TCP broken, UDP has stable connection but no traffic flows (ping = request timed out)

ProtonVPN TCP/UDP

3.005: works
3.013: successful VPN connection terminates browser access & SSH connection *

VPNbook

3.005: UDP successful connection but no data flows (ping: connection timed out)
3.013: successful VPN connection terminates browser access / cannot ping router *