WebKitGTK 2.40.x stable has been available for a little while. The main new features are the stable GTK4 API, Speech Synthesis, async Clipboard API, new JS integration APIs, and WebGL2

The current version is 2.40.1: https://webkitgtk.org/2023/04/20/webkitgtk2.40.1-released.html

The recent security advisory also covers issues which were fixed in 2.40.1, more at: https://webkitgtk.org/security/WSA-2023-0003.html