Hello all!
I've only played the game for a few hours on the Switch and I am level 30+. I am trying to find where to do the challenger mode to unlock the challenger gear crates. I found a FAQ saying I need to be level 24 to play them. This is the only information I can find on this mode.

Unfortunately I can't find the challengers anywhere on the map. I've scanned each race icon to see if its there but nothing is showing.
Am I missing something that I need to complete before being allowed to do them?