Randall Tarly may be waiting for a Blackfyre to come again, but Aegon is a Targaryen (even if only just in name). If he is secretly a Blackfyre (or fraud of a different color), it’s a *very* small circle of people who know that and it’s not going to be announced publicly. So Randall Tarly is going to be waiting a long time. Now if he wants to publicly back a Targaryen (real or not), Randall may have some options.