Firefox for Linux changes the shortcut key for "Select All" from Alt-A to Ctrl-A for solving web-compatibility and avoiding conflict with access keys. If you want to keep using Emacs like key bindings, e.g., you configured your GTK settings to use Ctrl-A as a shortcut key for moving caret to beginning of a line, you must change ui.key.textcontrol.prefer_native_key_bindings_over_builtin_shortcut_key_definitions and ui.key.use_select_all_in_single_line_editor from about:config. Currently, these are disabled by default but will be enabled by default in a future release.
The Web Locks API landed. This allows scripts running in different service workers or tabs to coordinate with each other.
WebRTC library updated, bringing improved audio and video features for web conferencing applications.
Added CSS color-scheme support to allow web pages to indicate which color schemes they can be rendered with (for example, operating system dark mode).