Hello @kinou.1 and welcome to the Community :)
The STM32VLdiscovery is an old board which contains the ST-LINK/V1, which is not supported by CubeIDE.and that the CubeProgrammer cannot access via USB.
Would recommend getting another board. A possible option could be to use external debug probe and connect it on the 4-pin SWD header.
I advise you to look at this post.
Hope that this answered your question.
When your question is answered, please close this topic by choosing Select as Best. This will help other users find that answer faster.
Imen
In order to give better visibility on the answered topics, please click on 'Best answer' on the reply which solved your issue or answered your question. Thanks