Probably a silly question, but I can't figure out how to challenge someone in the INFINITY tournaments. I entered 2 of them and was INSTANTLY challenged in both, but I can't figure out how to challenge someone else.

Thanks!

Okay, I think I understand. Challenges are done automatically by the system it seems. Strange, but I think I like the idea.

This is correct. Challenges are automatic.

FAQ in menu links to documentation about each tournament type. I found it very helpful.

Go via their name, top right “invite”

Tournaments you are matched in a league