Hi, I tested recently this camera with RUT240, but I'm on 3g/4g PUBLIC IP and all working well with defaults video camera settings loaded and nat/portfowarding http and RTSP 554 from wan to lan or* with IPsec vpn.
I can manage hkvision camera (dome type full hd sensor) from Firefox Web browser, also I see Live image etc. no need Internet Explorer plugin with correct stream setup.
I can play video stream with VLC video player (Network url RTSP://user@password:IPorDDNShost)
If you get in trouble, you need to check camera setting first, next you can check firewall configuration of RUTos, and vpn connection is reccomended, you can build like IPsec client tunnel, Openvpn client, or ZeroTier from package manager allow you to estabilish a direct connection to your camera if you live under private IP from ISP.
A side note for firewall configuration of RUT240, I check it is full of "many" zones unconfigured and maybe you dont'want some type of advanced stuffs like GRE SSTP PPPTP L2TP, so you can edit "/etc/config/firewall" and clean up unwanted zones/rules with reasonable safety.
Today I clean successfully my firewall unwanted stuff, and after apply changes I see more fast responsive RUTos, all working good without errors.
vpn zone with option network commented
lan zone vith option network 'lan'
wan zone with option network 'ppp wan' instead of option network 'ppp tun wan wan2 wwan0v6'
In my scenario I want only modem ppp (wwan0) and wan (wwan0) from hardware modem onboard, You need to adjust as you needs of course all connections used by your site before deleting others.
If you not skilled enough, proceed with caution, make initial backup of configuration, because all system live on OVERLAY partition, if you do a reset (restore) to defaults, overlay partition will be erased at all and router replace with firmware stock rom configuration.
When you made a single change on config file section, deleting or commented out, if unsure of behavior, I advice to save file then go to Network>Filewall page and check you changes if it parsed correctly by the "uci" subsystem.
If not, and the browser show text onli error parsing information, you can easy revert your last change made.