So, given that Mango's ability is verifiable, I'm going to conclude that he probably isn't Scum with Ekko. Prof and Indigo believe that Worst *is* Scum with Ekko, which would of course mean that Mango and Worst are not Scum buddies.
My reasoning for this is as follows. For Ekko and Mango to both be Red Scum, we have one that can create chats and one that randomly joins them. Given that Mango doesn't join Ekko's chats, this would only serve to create doubt between their claims, which seems unlikely to me. I still believe Mango will need to be flipped, as he could be Blue Mafia, but a significant part of his scum case was him being with Worst, which currently seems unlikely to me. Food for thought.