I appreciate someone who has read 3 days worth of threads on the forum, but have you come across the free mesh VPN Tailscale? You don’t even have to run Tailscale on the OS5 because Tailscale on OS5 or another device (can be a $50 gateway or a PC) can act as a subnet router for routing OS5 NAS files with Wireguard end to end encryption and there is zero configuration for tunnel through CGNAT. Tailscale has its own multifactor authentication and does not rely on any WD relay servers or authentication servers.
Notice this Win10 desktop client below is on 192.168.0.41 via Wifi hotspot but able to use Win File Manager to access remote routing from the My Cloud Home which is at a remote location on 192.168.1.xx, copying >100 files in a folder from the MCH. This is also possible on macOS, Android, iOS and Linux. This is made possible by enabling a Tailscale Subnet Router in software or firmware in the 192.168.1.xx subnet. Instruction in the MCH subforum.
