A UKGC licence is the baseline. Check that RTP is easy to find, withdrawal...

https://blogfreely.net/teresa-long85/game-library-size-vs

A UKGC licence is the baseline. Check that RTP is easy to find, withdrawal times are clear, and responsible gambling tools - such as limits, time-outs and self-exclusion - are easy to use. These practical details can make the difference.