Is there any possibility that the Covid-19 virus can enter the body through the ear canal? If so, what kind of precautions should I take when inserting my HAs or handling them?
Very unlikely. Covid need a mucus membrane to penetrate. I really can’t see how the cerumen producing glands in the ear canal would do it. But keep in mind that this advice is worth exactly what you paid for it.
The only real risk would occur if the Eardrum is compromised. It then effectively becomes part of the upper respiratory tract.
I place my hearing aids in the D-dry each night. This has a UV sanitizing action. The outer ear canal is essentially skin. The virus needs to enter via the mucous membranes so the risk is highest by breathing it in or touching fomites(contaminated items) then touching your eyes, nose or mouth. Washing hands frequently, not touching your face and physical distancing are the cornerstones of protecting yourself. I do not touch my hearing aids when I am outside my home so that I remember not to touch my face. Carry hand sanitizer and use it before you touch the hearing aids so that your hands remain clean when near your face in case you touch your face at that time.