Thunderbird Will Phase Out Legacy Add-Ons, Will Support WebExtensions (bleepingcomputer.com)

Catalin Cimpanu, writing for BleepingComputer: Mozilla announced last week plans to modernize Thunderbird's codebase, plans that include fixing some "technical debt" by incorporating the recent changes in the Mozilla engine into Thunderbird, adding a new user interface (UI), and phasing out old legacy add-ons that are built on the XUL and XPCOM APIs. The changes are part of Mozilla's new plan for Thunderbird development, a project that it left for dead in 2012, but later decided to reinvigorate in 2016.