The delays were announced in blog posts on the respective games web pages, with Rainbow Six Extraction being pushed to January 2022 and Riders Republic changing from the 2nd September to the 28th October 2021.
A community message about the delay to Rainbow Six Extraction stated:
Our ambition with Rainbow Six Extraction is to deliver a full-fledged AAA experience that changes the way you play and think about cooperative games. With unique features like Missing In Action or The Sprawl, every mission is set to be a tense and challenging experience in which you’ll lead the elite operators of Rainbow Six in a fight against a lethal and evolving alien threat. We are embracing the opportunity to take additional time to bring this vision to life the way it deserves in January 2022. We are confident this will ensure Rainbow Six Extraction is the immersive, cooperative, and thrilling experience we set out to create, and the one you aspire to play.
Similarly, the community message for Riders Republic stated:
To ensure we can deliver the best game for all players, we've made the tough decision to delay our release date from 2nd September to 28th October. This will give us more time to fine tune the experience and give you another chance to jump in before launch and provide feedback. We’ll have more to share soon, stay tuned!
Both community messages end with a promise of sharing more information soon, leaving us only to speculate on the exact reasoning behind the delay until more information is released.