It would be more efficient to pay someone market rate, have needed work get done, and subsidize their existence than to try and offload that cost onto employers.
It also has consequences like increasing the attractiveness of substituting capital (i.e., automation) for labor or simply leaving some work undone (e.g., many smaller restaurants in CA are going out of business due to multiple government policies, including very high minimum wages).
The trick for this to work is that the UBI has to really cover a lot of basic needs.
Overall, this works better for lower skilled workers than it does for higher skilled and higher paid workers. But it could also make sense for people staying home to raise their children, a job which is not compensated today.
How would such a program even work? If we say the Maintenance Wage is $15, is the government just paying the difference between that and the market rate? If so, it seems the ideal salaries to offer are $0 (let the government subsidize it) and $16+ (but you could just get two $0 workers, so I'd expect pay scales to really start at more like $30?)
This seems like it rapidly descends into Bureaucracy or Communism