The Department for Work and Pensions outlined the rules around holidays while claiming Universal Credit.
If you go abroad, you can continue to claim Universal Credit for one month, so long as you are eligible for it, remain eligible while you're abroad, and inform your work coach that you're going. However, you cannot continue to claim Universal Credit if you move to a different country permanently, and you can't apply for Universal Credit whilst you're abroad.
If a close relative to you dies while you are abroad you can get Universal Credit for one extra month, but this only applies if it would not be reasonable for you to come back to the UK. So for example if you were visiting a relative who lives in another country and they passes away while you were there, you could get Universal Credit for the extra month, but if a family member in the UK died while you were abroad you could not.
