Let's get rid of some confusions here!
Electrical 'descalers' are not water softeners -- they do not remove anything from the water, they just 'condition' it so that (in theory) scale does not form and stick to metal surfaces inside water heaters. The conditioned water is still 'hard' and forms scum with soaps.
True water softeners (usually resin bed regenerative salt types) actually remove calcium and magnesium from the water leaving it 'soft' -- no scale is formed and it lathers easily with soaps. However the softened water is high in sodium and so should not be drunk or used to water the garden.
There are several types of water 'conditioners', including magnetic, electrolytic, radio-frequency, polyphosphate dosing, and others. Of these, the only one that I know that works -- from personal experience over many years -- is the polyphosphate dosing type. I have read research that shows the other types work under certain conditions, but I have seen many domestic installations where they have clearly failed to work (including in my own house). In these cases I have fitted polyphosphate types with proven success.