@Slowrunner 

Hi, thank you very much for your message.

I'm afraid there hasn't been a beta firmware for Archer NX500.

Can I have your SIM service provider?

Do you run into any issues with the current official firmware? Now all SIM ISPs use 464xLAT. So if the internet works well now, I don't think you need 464Xlat.

Wait for your reply.

Best regards.

Dear TP-Link Archer NX200 users, To add the VPN Client feature, the TP-Link team needs more user requests and votes on the thread below. Kindly support by voting or adding a comment.

https://community.tp-link.com/en/home/forum/topic/862578?replyId=1685664