Let me help here, I am from Meaco.
Since January 1st 2020 all dehumidifiers, fridges, freezers, wine coolers and air conditioners have had the same environmentally friendly refridgerant called R290. It is much, much better for the environment, but it is a member of the propane family, and it is flammable.
So it has these legal warnings, as do your fridges and freezers, which are in your kitchens already.
The gas has been designed to be heavier than air, so IF your dehumidifier, fridges or freezer develop a leak, the R290 will fall to ground. Your gas hob, boiler (and any cigarette you might be smoking) will be much higher up.
Also in the manual it said not to use the appliance in a room smaller than 4m² your kitchens will be larger than that (2m x 2m).
So there is no danger in using your dehumidifier, fridge or freezer in your kitchens.
Hope this helps to put your minds at ease.