If you want to use the AI features (and you do because they reduce false alerts to almost 0) then you need a recorder that passes on the intrusion messages. As far as I’m aware at the moment ONVIF are not certifying Dahua cameras fir fear of being caught up in the NDAA ban in the US. And most of the third party NVR solutions use the ONVIF files to add specific cameras to their systems. So currently Synology and QNAP do not support TiOC. Likewise, if you want a Dahua NVR (and you probably do) then you need to get one that is AI enabled so it passes the alerts on. Of the NVRs available today, the cheapest 4-camera unit is the NVR4104HS-P-4KS2/L which is about £150 plus a hard drive. The cheapest WizSense NVR (much better AI) is the 2104HS-P-I at about £155 plus a hard drive. If you go to 8 cameras then you’re looking at the same model designations but with an 08 as the 3rd and 4th digit. 16 cameras is 16 in those locations.
While Dahua are arguably still the best of the soft white cameras the Hikvision ColorVu are also really good, albeit with the proviso that they are also covered by the NDAA ban and as far as I can tell, none of their current range of recorders does what the Dahua WizSense ones do. But they have new ones coming out very soon. Sadly they seem to launch a new range every 3-6 months so it’s very hard to keep up. Wherever you buy from, just make sure they check your compatibility for you. Because they’re only supposed to be sold to certified installers they’ll sell you anything and while they’ll be very sympathetic when your system doesn’t work, they won’t swap it out if you order the wrong thing!