Have you tried the IRS online tool for amended returns?

https://www.irs.gov/filing/wheres-my-amended-return

I don't know the source of the 24-month claim.  The latest from IRS is,

"As of January 1, 2022, we had 2.3 million unprocessed Forms 1040-X. We are processing these returns in the order received and working hard to get through the inventory. The current timeframe can be more than 20 weeks instead of up to 16."