UPDATE:
A solution to the authentication issue will ship with version 102.7.1, releasing during the week of January 23.

Version 102.7.0 is now available for MANUAL download only, to allow unaffected users to choose to update and benefit from the fixes it delivers (https://www.thunderbird.net/en-US/thunderbird/102.7.0/releasenotes/)

Please note that automatic updates are currently disabled, and users of Microsoft 365 Business are cautioned to not update.