For people curious as to why AOC suddenly support UBI (not Yang). Just my speculation,

To remind everyone, AOC had openly compare UBI as a "Trojan horse", "gut welfare" rhetoric in return to advocate an different alternative, the FJG which Bernie endorse. In this case, she applies political tactic to persuade Bernie former supporter ( who is was supporting yang) and to provide confident for Bernie main base.

Now since Yang had dropout (safe to talk about ubi) and endorsing Biden recently. Suddenly and i mean immediately, AOC supports UBI. This is a political motive, it lures back some former supporters who are NOW disappoint of Yang's irrupt endorsement.

in short, political motivation, not something she genuinely care about. as so with much coincidence timing, this becomes more certain.