Is a stair lift installed to provide palliative care a medical tax deduction for the patient AND also a home modification deduction for homeowner who installed it?

Yes, you are able to claim an installation for a chair lift as a medical expense.  Depending on the province, you may also be able to claim a home renovation credit.  Please see the following link for more information, https://www.canada.ca/en/revenue-agency/services/tax/individuals/segments/homeowners/provincial-credits-grants-you-claim-on-your-tax-return.html.