This is the second article in the “What’s new in Qubes 4.1?” series. You can find the previous one (about GUI Domains) here. While the introduction of GUI domains is a big, singular feature, the changes to qrexec are more complex and varied — but also very important.
This is a companion discussion topic for the original entry at https://www.qubes-os.org/news/2020/06/22/new-qrexec-policy-system/