I've been looking and reading everything I can find.
Looks like for 2021 you DO need to have some 2021 earned income. See IRS Pub 596 Eligibility Checklist on page 32. Step 6 says "Is your total earned income at least $1 but less than……." And you have to answer YES to everything on the Checklist.
And page 2 Table 1 Rule 7 says you must have earned income. See Rule 7 on page 8.
IRS Pub 596
https://www.irs.gov/publications/p596
