I originally registered on blued in 2018 in Thailand or Taiwan, but I have been using it in Europe for months without problems (but density of profiles is low in Europe).
Firstly, some programs can disable screen shot by software.
Secondly, you have to keep one or two fingers on the screen to keep seeing the picture.
In a few cases, I circumvented both by taking a screenshot with my camera (or second mobile phone), but it's cumbersome and the picture is of lower quality.