Of course! Detergent is optional. The addition can also be deactivated. And there's no fill level sensor either.
Also important: you can simply open the cartridge and pour in your own liquid. Of course, it should not foam and should be suitable for robots in some other way.
I use a terracotta cleaner from Lithofin, for example, which works wonderfully, I've already used 1 litre.
Of course, it's up to you which product you use.
But the original one is incredibly expensive and hard to get in Switzerland

Correct, washing is also possible without detergent.