The Brothers' War Update Bulletin is the place to find information about changes to the Magic Comprehensive Rules that are coming with the set's release. This document is written while the rules are still going through editing, so it's possible they'll be a little different from the final changes. When the rules are finalized, you'll be able to see them on the rules page. Normally, this is also where you'd find updates to the rules text of some older cards, but there are no updates to the Oracle text of older cards alongside the release of this set.
First, a note from Jess Dunks:
Hey, everyone, it's your friendly Magic rules manager here! I'd like to take a moment to introduce Eliana Rabinowitz, the author of this set's update bulletin. She's both a Magic rules aficionado and one of the talented game designers that I work with closely to make Magic. Moving forward, this update bulletin may come from either of us.
Alright, let's dive in!
Comprehensive Rules Changes