The main storyline of Pokemon Scarlet and Violet's Indigo Disk DLC will take you to Blueberry Academy. There are four trainers you'll need to take down in the Terarium that are part of the BB Elite Four. You'll eventually face off against Amarys and her team of (mostly) Steel-type Pokemon in the Canyon Biome.
Pokemon Scarlet & Violet: How to Beat Amarys (BB League Elite Four Trial)
Amarys has a team of tough Steel-type Pokemon up her sleeve in Scarlet and Violet's Indigo Disk DLC.