I'm sorry to hear of your loss.
When you are preparing your mother's return, since she lived in Quebec, you will enter her province as Quebec, and have access to the Quebec forms.
Please note that TurboTax Online does not currently support form T1255 - Designation of a Property as a Principal Residence by the Legal Representative of a Deceased Individual. So if your mother own a home (principal residence), then you would have to use TurboTax CD/Download (for Windows 10/11) in order to use the form T1255. TurboTax CD/Download can be purchased directly from TurboTax.ca