Hi Julien,
Unfortunately, only the modern SharePoint list support to be created based on an Excel Template.
Hence you might won't be able to create an Issue Tracker from your Excel Template.
The truth is, Issue Tracker is nothing but a customized SharePoint List. With that said, you can actually customize the normal list to achieve most of the functions in the Issue Tracker.
Could you let us know which functions do you need, so we can help you customize your current list?
Regards,
Alex Chen