I’m a little late to this party because all my main Macs are running macOS 12 Monterey, but about two weeks ago, Apple quietly released macOS 11.6.7 Big Sur separately from other updates. The release notes are the first since macOS 11.5 that provide any useful detail, noting that the update fixes a problem in macOS 11.6.6 with opening email attachments if the app required to open the file was already active. Users received error messages claiming they didn’t have the necessary permissions.
TidBITS Talk user chs had trouble printing after updating to macOS 11.6.7 on an M1 MacBook Air; it seems that their installation of Rosetta was removed as part of the update such that they had to reinstall it to enable the Brother printer driver (although an update to the native Brother software might also have resolved the issue). Will M also noted that, after updating to 11.6.7, Time Machine completed the first backup to his Time Capsule since he had installed 11.6.5 in April.
In short, for those still using Big Sur, it’s worth updating to macOS 11.6.7 using Software Update to address the email attachment bug and potential Time Machine blockages, but beware that you might need to reinstall Rosetta. Or just make the jump to Monterey.