I do not think they ever finalized the 2015-21 safe harbor act (reference to using Revenue Procedure 2015-X).
I think the correct method, for session reporting, is to attach IRS FORM 8275 with the following language:
"My reported gambling winnings don't match the W-2G total because I used session accounting to arrive at the total for winnings, as per Chief Counsel Memorandum 2008-011 and Shollenberger v Commissioner, which established that wins and losses should be tracked by session, and that 'The Form W-2G that reported their gross winnings from the $2,000 jackpot should not be reported on line 21 as $2,000"
If you want to read every article & reference on this subject of gambling session reporting:
https://easy.vegas/gambling/taxes
This person has compiled EVERY source & article on this complex subject.
Also, most recreational gamblers may not know they can deduct "expenses incurred in connection with the conduct of the gambling activity, such as travel to and from a casino" - see IRS PUB 529 (DEC 2019), Section Gambling Losses Up to the Amount of Gambling Winnings.
