I've browsed enough on forums/FAQs/social media about how I could delete these imported brushes (I got those from the new update). The other answers here only work on computers but I can't find a single answer for deleting brushes in IOS devices (iPad/iPhone). Since I think it is a new version still, can you please help? I'm sturggling to clear space on my iPad and delete other imported brushes.
Right now brushes cannot actually be removed inside of Sketch. They must be deleted either through the Libraries tab in the Creative Cloud Mobile App or by logging in with your Adobe ID to https://assets.adobe.com/assets/libraries and deleting them there.
Just remember, if you delete the entire library, the deletion will be permanent. It is, however, possible to go into the library and Archive (then later Delete) one brush at a time.
I hope this helps.