I noticed when working on my objects which consist of multiple smaller parts, that when I already unwrapped them and now want to select some objects with L it will only select the UV island but not the whole object anymore. Is there another operation I have to use now or a button to press to let blender know that I do not want to select UV islands but the whole mesh?
Select Linked has options in the Last Operator panel (once it was executed).
Often by default Seams option is checked which means selected linked geometry will be limited with the seams added to the mesh:
This is useful for selecting only one UV island within the current mesh without picking seams manually.
To disable that uncheck Seams and all the linked geometry of the mesh will be selected.