How? Toho produces a lot. Dr. Stone by IMS, Little Witch Academia from Trigger and Himoto Umaru-chan from Doga Kobo are all them. Plus both of Orange's big shows (Beastars and Land of the Lustrous). Going through their Youtube channel they work with PA Works a bunch too.
I’m just going by the studios they seem to work with the most. It of course can be a lot of other lesser known studios.
I didn’t include Orange because they seem to be focused on CG series currently, and it’s unlikely Jujutsu Kaisen will be CG.
And Trigger has little to none manga adaptations, and mostly does original anime. And if they decided to adapt a Jump manga I highly doubt Jujutsu Kaisen would be the one they worked with as it doesn’t fit their style at all.
I’m also going by the fact that
1. Bones is currently adapting a Jump series, so why not another?
2. Jujutsu Kaisen is a pretty popular title, so I think the odds of it going to bigger studio is more likely.