I think he fought a legitimate boxer before and it was against Tommy Fury, unfortunately he loss, so most probably he won't fight a legitimate boxer because he already experience losing and that will not help if he wants to grow his career. His popularity is really high, that is even despite he is not in a championship yet, even more popular than a boxers who are in a championship fight.
Tommy is hardly a professional boxer though. He might have a 10-0 record (including Paul) but he hasn't fought any higher ranked fighter yet. On top of that, it doesn't look like he's too much interested in serious boxing career and in moving up the ranks, as his next opponent is Olajide William Olatunji (aka "KSI"), some other "social media influencer" (which I only know from getting KO'ed by Jake Paul). So it's evident he's in it for the fame/money not for the sport.
But yeah, that was the closest to a real boxer Jake Paul has ever faced. I think there's a big chance he'll get whopped by Mike Tyson in July, despite Tyson being 58 at the date of the fight.
Its funny how people consider him being a heavyweight, when he weight less than Usyk, who had to gain to be a heavyweight 
