Last week, Apple released OS X 10.11 El Capitan. Due to a widespread networking issue between my ISP and Apple, it took several days for me download and install the latest operating system, which resulted in a delay in updating the compatibility of Delete2Archive.
Before providing instructions on how to update Delete2Archive, I should mention that after limited testing my Gmail accounts continue to work properly in Mail without the need of the plugin (as they have since OS X 10.9.2). If you’re still using Delete2Archive, I strongly suggest you test your system to see if you can get your Gmail accounts archiving natively. Specifically, you can try unchecking the “Move deleted messages to the Trash mailbox” option under Preferences > Accounts > Mailbox Behaviours.
For those that still legitimately need the plugin, it has been updated for compatibility with OS X 10.11 El Capitan. Follow the installation instructions and download the new version of the plugin from the Delete2Archive page.