The answer to this question is not straightforward. Some of the new casino sites have a UK license, while others don't. We can't say that all new casino sites have a UK license, but we can say that many of them do.
This is because some of the new casino sites are licensed by the UK Gambling Commission and others are licensed by other regulatory bodies in different countries. Also you can read this article: https://pressfrom.info/uk/news/tech-science/-561855-do-all-new-casino-sites-have-a-uk-license.html