Money is a social construct, not some kind of physical quantity subject to conservation laws, and can be and is introduced into the economic system all the time. The real question is really would introducing more money or a UBI cause social disruption by e.g. disrupting price signalling by high inflation or changing incentives to work so less goods and services that people actually value are produced.

It is a social construct but if you just print money you get ... inflation. You can't just increase money supply to redistribute wealth without consequences.