http://www.theidolpad.com/2021/12/ai20-showcase-round-top-59-standing.html
Note: It's not necessarily an exhaustive list, but it should be very close to it. Also, it does not guarantee that a contestant advanced.
While the judges otherwise refrain from commenting after the performances during the showcase round, Katy Perry made an exception when she repeatedly compared Elliot Greer to Vincent Van Gogh, following his performance of an original song.
All 3 Judges:
Allegra Miles
Christian Guardino
Danielle Clavell
Elli Rowe
Elliot Greer
Hunter Girl
Jacob Moran
Jay Copeland
Katyrah Love
Kelsie Dolin
Kenedi Anderson
Kezia Istonia (a.k.a. Lady K.)
Leah Marlene
Lexi Weege
Nicolina Bozzo
Noah Thompson
Sage
Sir Blayke
Tobias Hill
Only Lionel Richie:
Briggs
Ryan Argast
Sam Moss
Scarlet Ayliz
Yoli Mayor