Final 5500-EZ and numbers for section 5

Two person Solo 401(K) for a Husband-Spouse Partnership LLC.
Filed 5500-EZ first time for 2019 as the plan assets crossed $250K first time.
Closed the LLC 12/31/2020 since could not sustain due to Covid-19. As of 12/31/2020 there were assets.
In June-July 2021 Rolled over to IRA for one partner and Transferred to workplace 401(K) for the other partner with a W2 job.
There are trailing dividends coming through.

When do I file the final Form 5500-EZ?
File 5500-EZ for year 2020 as Final OR File 5500-EZ for year 2021 as Final, with 2 participants [5a(1)&a(2)]at the beginning of the year 2021  and zero [5b(1)&b(2)]at the end of year 2021? If Final has to be for 2021, what is the deadline?

Thank you!

I am a newbie. Gurus please help me out with your suggestions. Thank you!

Page 3 of the instructions are very clear.

https://www.irs.gov/pub/irs-pdf/i5500ez.pdf

Final ReturnAll one-participant plans and all foreign plans should file a return for their final plan year indicating that all assets have been distributed.Check box A(3) if all assets under the plan(s) (including insurance/annuity contracts) have been distributed to the participants and beneficiaries or distributed or transferred to another plan. The final plan year is the year in which distribution of all plan assets is completed.

The final year ends the last day of the month the assets leave the plan.    You count the normal filing deadlines from that month.

So 2020 can't be the final year as there were assets in the plan. 

Thanks a lot!!💐

Are the dividends shared between the participants or are they individualized?  My thought being, if you can get those dividends to automatically post to the IRA instead of the original plan account, then you could already be down to zero for the final time without having to wait any longer.  It would be less easy to do with money due to a different 401(k) plan, though.