Code 1L means you took $ from your 401k as a loan.
401k loans are not subject to income tax (or a penalty) and therefore the CARES Act 3 year income program (8915-E) does not apply to you (as you have already "avoided" both the tax and the penalty).
But, if you cannot repay it, contact your 401k plan administrator and have them file the paperwork to change the coding, to alleviate you of a required loan repayment and to ultimately issue a new 1099-R (with a code 1 which is early distribution). Then, you can proceed with TT which will file the 8915-E to deal with the penalty and resulting taxes.
