There is no time limit to amend.
The time limit for refunds (or for the IRS to assess tax) is three years, not two. That means 2021 can still be amended and get a refund.
For 2020, you won't be able to get a refund. However, in the event the rental had a loss and that loss was suspended due to the Passive Loss rules, then you can amend 2020 to carry the increased Passive Loss Carryover to 2021.
