Thunderbird 128 features many underlying code improvements, including the transitioning to using more Rust code within the mail client. Thunderbird's Rust adoption remains an ongoing effort.
Thunderbird 128 also brings UI/UX enhancements like a redesigned cards view and enhanced folder pane. Thunderbird 128 also offers better theme compatibility and support for accent colors on modern desktop Linux distributions.
Downloads and more details on the Thunderbird 128 release via the Thunderbird.net blog .