BlueCherry is another multi-camera Linux NVR.Here is a great 45 minute overview and demonstration. Below is mainly just the stuff not really covered in it.
You can download their client and connect to their demo server to try is for yourself. Note only 4 of the demo cameras would connect for me and one is playing a animated video.
Interface beats Zoneminder by a mile.
Their feature compare with Zoneminder is here. kerberos.io does beat them on some features like heat maps but over all I'd say the Bluecherry interface is better than kerberos.io too.
Does most of what Blue Iris does. Main diffs with Blue Iris
It costs a lot more.To dup my current 38 cam set up would be $650 to 675 vs $135 for Blue Iris. There is a 30 day free trail though.
Generally the interface is not as polished as Blue Iris though way ahead of Zoneminder
Plays back at up to 128x where Blue Iris does up to 256X
Probably not that big of a deal unless you are having to find when thing X happened in several hours of video.
Also not seeing many automation options.
For example with Blue Iris I can trigger virtual devices in my home automation system based on motion and loss of signal. Here the only option appears to be email. This is what the options are with Blue Iris for motion or loss of signal triggering.
Motion detection seems thinCompare this Bluecherry screen to Blue Iris' screens
Zoom seems to stay centered on image instead of cursor location like in Blue Iris
This means if the thing you want to zoom in on is off center, zoom is basically useless. Also it is a simple +- button system of step instead of the much smoother Blue Iris method of put your cursor over the subject and use the scroll wheel to zoom in and out.
Not sure about loads since I have not set up a sever to test on matching hardware. The client did not seem to load my PC much at all though all I could pull from their server appeared to be 4 streams around 720p.