What do you need the 2019 AGI for? You only need the 2020 AGI to efile this year.
2019 AGI is on 1040 line 8b
How to Access prior year online returns
https://ttlc.intuit.com/community/prior-year-return/help/how-do-i-access-my-prior-year-return/00/270...
If you can't get the side menus to open up to access the prior year..... You need to start entering some basic Personal Info in 2021 for the side menu to open up. Just continue a little ways into 2021.
Or request a transcript from the IRS
https://www.irs.gov/individuals/get-transcript
