What happens to an estate in Saskatchewan if there are no relatives?

This answer covers the law of Saskatchewan.

If someone dies without a will and has no relatives who can act, the Public Guardian and Trustee steps in as Official Administrator, the 'administrator of last resort'. It acts where there is no next of kin or the next of kin cannot act. It generally does not act on estates below $25,000 or where a relative is able to administer.

Before an estate is treated as having no heirs, the search matters. The right to apply to administer goes first to a spouse, then children, grandchildren and other issue, parents, siblings, nephews and nieces, next of kin of equal degree, creditors, and finally the official administrator. If beneficiaries cannot be found, an heir locator may be hired, and if that fails the administrator must apply to court for directions on paying out the funds.

Which Act decides who inherits depends on the date of death, with a different Act for deaths on or after October 1, 2019. Whether and how the Crown may take property that no one can claim is a legal question that depends on the facts, so confirm it with a lawyer before assuming anything.