The GNOME Design team dropped many icons they deemed “legacy” in the 42 release. There have been further icon removals since then. This has been complicated to manage in both Ubuntu and Debian since we don’t want to break apps that were using icons that previously appeared to be stock icons.
We are now after User Interface Freeze for Ubuntu 23.10, but we do plan to land adwaita-icon-theme 45 soon after we open development for 24.04 LTS.