The two pieces of evidence that would be most relevant to the claim that some young people now aspire to be YouTubers instead of movie stars or professional sports players are:
B. a quote from a young person about what it would be like to make a living from YouTube - This provides direct insight into the aspirations and motivations of young people regarding their career choices.
F. two polls spaced twenty years apart that asked young people about their dream careers - This would demonstrate a change over time in the career aspirations of young people, highlighting a shift from traditional dreams like movie stardom and sports to YouTube stardom.
Together, these pieces of evidence directly address the changing aspirations of young people regarding their desired careers.