Do I need to amend my 2020 return, since I entered it in the "Other self-employed income including cash, checks, Form 1099-K, etc." section?
Yes. If 2020 was the first year you started renting this property, you need to complete amending the 2020 return before you can even start your 2021 return so that depreciation is started properly to ensure it's correctly carried over to the 2021 return. Absolute perfection in that first year as a landlord is not an option - it's a must. Even the tiniest of mistakes can (and will) grow exponentially over time. Then when you catch the error years down the road (usually the year you sell the property) the cost of fixing it *WILL* be expensive.
