I'd contact Nord VPN to see what they support and work on. It can't be installed on the router though.
My Setup | ISP SparkLight | Internet Cable 1000↓/50↑ CAX30 Gateway Mode | Wifi Router and RBK853 | Switches NG GS105/8, GS308v3, GS110MX and XS505M |
Additional NG HW: C7800/CAX80/CM1100/CM1200/CM2000, Orbi: CBK40, CBK752, RBK50, RBK853, RBK752, RBK953, SXK30 | NightHawk: MK63, R7000, R7800, R7960P, R8000, R8500, RAXE500, RAX50v2, XR450/500/700/1000, EX7500/EX7700
