If we are talking about an idealized world with spherical consumers and a single product, then yes. However inflation is a scalar measure of the development of

If we are talking about an idealized world with spherical consumers and a single product, then yes. However inflation is a scalar measure of the development of the prices given some basket of goods. An UBI will change what stuff people buy hugely. The economy will need to shift around a lot to accomodate that. Any use of a "steady-state" model is really inappropriate and you can't draw any conclusion from that.