No solo activities or sub-units have been set up yet. Their contract ends next year, it'd take a long time for a 9 member group to create official solo activities and they haven't done anything yet. Their collab with K/DA was the closest we got to a sub-unit (I thought it was pretty cool that Jihyo likes playing LoL and she collaborated with their group along with Nayeon, Sana, and Chaeyoung) and Momo's appearance for her friend's song wasn't technically a solo project, it was something to do for her friend and to support her (which was very sweet).
If they were going to have solo projects, this is the ones I could see them doing:
Nayeon: Modeling or Soloist
Jeongyeon: Possibly Acting
Momo: Dancing (maybe like Lisa's Lilifilm)
Sana: MC/Variety Show Host or YouTuber
Jihyo: Soloist, maybe acting
Mina: Gaming channel LMAO
Dahyun: MC/Variety Show Host
Chaeyoung: Rapper/Lyricist
Tzuyu: Modeling maybe acting
