Analysis of information sources in references of the Wikipedia article "Didymus the Blind" in English language version.
These references clearly show that Didymus considered 2 Peter genuine. That he considered the book canonical is borne out by other references in which, for example, he introduces a "proof" from 2 Peter with the standardized Scriptural introduction (D. Zech. 79:2), and, especially, in which he argues "from the Scriptures" that there are fallen angels, quoting 2 Pet. 2:4 (D. Zech. 9:30ff).
These references clearly show that Didymus considered 2 Peter genuine. That he considered the book canonical is borne out by other references in which, for example, he introduces a "proof" from 2 Peter with the standardized Scriptural introduction (D. Zech. 79:2), and, especially, in which he argues "from the Scriptures" that there are fallen angels, quoting 2 Pet. 2:4 (D. Zech. 9:30ff).