The 10 year RMD rule for non-spousal inherited IRA's was part of the legislation in the Secure Act of early 2020. This rule is now subject to a language interpretation and also will have a new public comment period to formalize "the rule".
The below article provides some information; as well as a link to the current IRS Pub. 590-B
I will attempt to keep track of this rule change going forward, but solicit others here to provide information as discovered.
Note example: For our house, part of a written plan instruction was that: One has 10 years to "take" all of the monies from a non-spousal inherited IRA; meaning that all of the money could taken in year 10, if desired. The "new" rule meaning would require RMD's for years 1-9, with the balance taken in year 10.
Secure Act, Ed Slott article