Do you need the salinity probe feature.
My previous watrermaker had one, but for this boat, I specified a completely manual system.
I always smell and tase the water before diverting it to the tank. I usually also use a hand held salinity meter.
It is really not difficult to do and keeps everything very simple.
There is place for a more complex fully automatic system, on a large yacht, but its just one more thing to go wrong and the salinity probe will not pick up Hydrogen Sulphide.
If the salinity probe fails use your wonderful human taste and smell sensors. Not even Tellie can fix those, but they rarely go wrong
A back up HH TDS probe will give you an objective measurement. These can be easily and cheaply replaced if they fail.