You’re supposed to post a clean lap on any rivals event, however, that does not work.
To unlock it, challenge a rival who has a flagged lap, hit a wall as you’re driving so your own lap is also flagged, then make sure you beat your rival. When you exit back out to the free roam, it will unlock.
I did this one last night and it worked. Coming second place in a showcase also worked for the other one. Ridiculous that we have to use the work arounds but hopefully they get it fixed soon and don’t mess up our progress while doing it…