Do I have to distribute 100% of my non-spousal inherited IRA within 10 years if I inherited it before 2020? the original owner did not take any distributions.

You can use your own life expectancy to determine the amount of withdrawal. 

The 10-year rule only applies with respect to decedents dying after 2019 (or after 2021 for governmental plans)

For an IRA inherited before 2020, your choices were to withdraw it over five years, (five year rule)  or to withdraw it over your lifetime.  If you did not withdraw all the money in the first five years, then you are deemed to have automatically chosen the lifetime rule.  You can withdraw more if you want to, but you always must withdraw at least your own RMD each year.

What Opus 17 described applies if the decedent died before their Required Beginning Date for RMDs.  Since you said that the original owner did not take any distributions, I suspect that Opus 17 inferred that the decedent indeed died before their RBD.