Purging performance-reducing tracker-extract caused other issues

You followed the wrong approach to disable tracker. In Ubuntu 20.04 and up, the file manager nautilus depends on tracker. So removing tracker automatically uninstalls nautilus as well. And since the Gnome Shell desktop icons extension depends on nautilus, that is gone as well.

A fool-proof way to restore all your Ubuntu desktop components may be to reinstall the ubuntu-desktop package (which is gone too):

sudo apt install ubuntu-desktop`

This will restore your File manager, your desktop icons, and any other Ubuntu desktop compound you may have removed.

To disable Tracker, follow the right approach.