I am an Italian noahide.
I wonder if Halakhah allows Gentiles to cremate bodies. My personal opinion is that this practice does not violate Noahide Laws, as it is not included in one of the relevant seven categories of commandments. I do not see a conduct that violates the prohibition against idolatry because, at least in the Mediterranean tradition to which I belong, the ancient pagan populations at some point abandoned cremation to use the burial (see for example the Romans and the Greeks), while maintaining their polytheistic cult; therefore cremation was not a peculiar characteristic of such cults.
I would also add that, even admitting that cremation means contesting the belief in the resurrection of the bodies (and I do not agree that those who decide to be cremated do not necessarily believe in the resurrection), Halakhah does not foresee any obligation for the Gentiles to believe in bodily resurrection, merely saying that the "righteous among the Nations", if observe the seven precepts with the conviction that HaShem has revealed them in the Torah,they will deserve a part in the World to Come (Rambam's Mishneh Torah-Hilchot Melachim 8:11 ).
Obviously I am referring to the case in which the decision to be cremated is not one adopted by the Gentile with the aim of making cult in this way towards one or more idols.