What is the ruling on purchasing insurance when buying a travel ticket to obtain the benefit of changing the departure or return date or canceling the trip due to an emergency, and is this considered permissible gharar (uncertainty/risk)?

If the insurance company is commercial and not based on mutual cooperation (takaful), then it is not permissible to deal with it, as it involves gharar (definition) (excessive uncertainty) and gambling. This is a significant and unforgivable gharar, as stated by the Islamic Fiqh Academy.