Basic income is historically no socialist idea. It's a liberal idea. Milton Friedman came up with it under the name of negative taxation.

Billionaire Götz Werner did a lot to promote the concept. In Germany the CDU (right-wing) politician Dieter Althaus spoke for it. YCombinator who invests into research in it is also no socialist institution.

Socialism is about workers rights. People who don't work but just receive basic income aren't workers. The unemployed aren't union members. Unions generally want that employers take care of their employees and believe that employeers should pay a living wage and that it's not the role of the government to pay low income people a basic income.