I'm not sure why you all ignore Rev Proc 2019-38 which was the final rev proc on the subject issued in September of 2019.  IRS Notice 2019-17 (issued in April of 2017) is just a PROPOSED rev proc.  While the proposal contained a signature requirement, the final rev proc did not.  It just says that the original timely filed return mus include "a representaion"  that the requirements of the rev proc were met.   The notice 2019-17 says that the statement must be signed  “Under penalties of perjury, I (we) declare that I (we) have examined the statement, and, to the best of my (our) knowledge and belief, the statement contains allthe relevant facts relating to the revenue procedure, and such facts are true, correct,and complete.”  That language is nowhere in Rev Proc 2019-38