On Windows only, after installing any of the DeskPack 20.0.1 plugins for Adobe Illustrator 2021, more specifically version 25.1 (Adobe's January 2021 update), you will no longer be able to find the Illustrator Eyedropper tool in the toolbar.
Illustrator's Eyedropper tool appears missing from the toolbar after installing Esko Data Exchange or other DeskPack plugins.
It has been fixed in DeskPack 21.03.
A possible workaround is to remove the Inspection Setup plugin whose tool is grouped with Eyedropper. A similar issue also exists with the Notes tool (also grouped with Eyedropper) which comes with PDF Import, here the workaround is to remove the Notes plugin.
The mentioned plugins reside in C:\Program Files\Adobe\Adobe Illustrator 2021\Plug-ins\Esko\Data Exchange\Inspection Setup and C:\Program Files\Adobe\Adobe Illustrator 2021\Plug-ins\Esko\Notes.
After removing the plug-ins and restarting Adobe Illustrator, you may need to "Reset" the toolbar. At the bottom of the toolbar:
Click the three dots.
In the upper right corner click the Prefers button.
The Eyedropper tool should now appear in the toolbar.
If any of the two plugins are required, then you should downgrade Adobe Illustrator to v25.0.1 or v25.0.