I realize, this seems to two different questions. The "extension" in 2020, or of 2020. So, I will offer this article, as well:

https://www.hiscox.com/blog/2021-federal-tax-deadlines-for-your-small-business

The nice thing about these, this late in the game for tax year 2019 (filing due in 2020) and tax year 2020 (filing in 2021), is that a web search offers all the pertinent data, as long as you find the IRS or other info is dated after retroactive bills were passed, for Fed and for the specific State(s) you need to file.