No, a signature is not always required for donating inherited stocks.
You can delete Form 8283, and go through the interview questions for your donation again. You can use the 'stepped up' value of the stock instead of $0 for Cost Basis. Use 'Average Price' as valuation method for inherited stock. Here's How to Delete Forms in TurboTax Online.
You're correct your stock donation should appear in Section A on Form 8283.
Here's more detailed info on Form 8283.
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