Will the difavtomat work if there is no ground?
To work, such a scheme will work, but keep in mind that you can’t do this, if only because in the event of zero burn-off, hazardous voltage will appear on the cases of all electrical appliances! It is better then not to connect anything to the grounding contacts of the outlets. Dif will work without the earth, if you touch the phase or the housing on which it appeared and you will not be killed by electric current (DO NOT CHECK IT!)
In more detail, we examined the issues of connecting diffavomats in the articlehttps://my.electricianexp.com/en/kak-podklyuchit-difavtomat.html