I'm surprised that non-Hikvision cameras are being complained about as a 'Language Mismatch', especially over ONVIF.
Are HJT cameras in any way linked to Hikvision?
If you would be happy with continuous recording - you could try connecting them as Generic RTSP with your Custom Protocol,
I think you've already seen the RTSP URL in ONVIF Device Manager, at the bottom of the Live Video page.
In the NVR, you've need to use the section starting with and including the '/' as the path - ie take off the RTSP://<camera_IP_address>
What firmware revision is on your 7608N-K2 ?
Oddly - I found that on firmware 3.4.91 the usual Language Mismatch over ONVIF for a CN DS-2CD3335 camera was not present, and the camera connected OK. But that may just be a bug with the Hikvision version of a language query over ONVIF.