For some who are planning to return funds, there could be tax advantages to doing this prior to December 31. (I should note that I have no inside knowledge about the process above and whether returning the monies prior to December 31 is even possible.)
In many parts of the US, you can get a referral to a lawyer for an initial consult at a low cost, and I think for some individuals and for-profits it may be worth a quick consult with a tax lawyer to ask whether there are different tax consequences for you of returning funds before vs. after December 31. I agree with Molly that you will want to work with a bankruptcy lawyer if you decide to return the money.
While I can't give any legal advice other than "consult a lawyer who can represent you," one potential scenario that comes to mind involves any US persons for whom the grant would be considered self-employment income that would count for 2022. Having self-employment income in 2022 and an offsetting business loss when the funds are repaid in a later tax year could potentially lead to a situation where you have to pay self-employment taxes in 2022 (i.e., Social Security/Medicare) and won't get a benefit from the later-year repayment (for self-employment tax purposes). I'm not confident in that assessment, but do encourage people who think they would have to pay self-employment tax on an unreturned grant to consider talking to a tax lawyer about that specific point very soon.
Thank you for the helpful announcement, and for all of your other work on this!