Is it legal for the military to demand the provision of civilian housing for ...

Yes, there is.

According to Article 8, Clause 17 of the Law "On the Legal Regime of Martial Law" in Ukraine or in some of its localities where martial law has been imposed, the military command together with military administrations (if they are formed) may independently or with the involvement of executive authorities, the Council of Ministers of the Autonomous Republic of Crimea, local self-government bodies to introduce and carry out, within the limits of the temporary limitations of the constitutional rights and freedoms of man and citizen, as well as the rights and legal interests of legal entities, provided for by the decree of the President of Ukraine on the introduction of martial law, such measures of the legal regime of martial law as establishing for physical and legal entities military housing obligation for the quartering of military personnel, members of the rank and file of law enforcement agencies, the personnel of the civil protection service, the evacuated population and the accommodation of military units, units and institutions.