There is an almost infinite number of models and policies a country could implement to address wealth inequality, and UBI would be at the bottom of that list in terms of effectiveness. UBI is not the tool for that job. Depending on the country you’re talking about and their current economic and monetary situation, you could… introduce legislation that restricted CEO incomes to a maximum percentage greater than a companies lowest paid employee? … increase tax rates on large accumulated wealth sums over a certain threshold like trusts and superannuation? … Increase taxes on sources of wealth that aren’t direct wage income, which is how most wealthy make their money in the first place? … Criminalise price gouging by preventing a company from raising prices when they have posted a profit in the last financial year? Literally thousands of more sensible and effective things you could change that would have a positive impact on addressing wealth inequality.