Retirement tax questions

I have been reading things for the last month regarding this matter and still am confused regarding the RMD. The Morningstar article, from the example, let me to believe it would be based on my life expectancy.  But when I look at the IRS it is unclear.  Vanguard does not support RMD for inherited IRA's and stated I should consult an accountant.  I was hoping someone on these posts would know the answer. 

 

My mother died at the age of 89 in 2020, her RMD was taken in 2020 as needed.  I am an adult daughter, when the Secure act does go into effect is the RMD based on my mothers age of 89 or mine? It makes a large difference in amount.