Form 5558 E File

I am finding conflicting advice as to whether Form 5558 e file is mandatory, if the Plan Sponsor otherwise has 10+ W-2's, 1099's etc that they file.  I realize that e file capability became a reality last year.  My question is, is e file mandatory when the Plan Sponsor has 10+ information returns that it files.  Thank you.

The instructions for the 5558 don' say anything about being mandatory but do say:

What’s New
Beginning January 1, 2025, Form 5558 can be filed electronically
through EFAST2 or can be filed with the IRS on paper.

and the IRS website also says so:  https://www.irs.gov/retirement-plans/form-5500-corner

Thanks Paul.  I looked at the instructions before I originally posted, and noted they're silent on any e file requirement.  Out of curiosity I looked just now at the 1099-NEC instructions and they do specifically cite the e file requirement.  I realize we can't rely on IRS instructions as being law.  There are several public commentators (CPA firms for example) that are stating e file is mandatory for Form 5558.  I realize they don't necessarily know the law either.  I understand the IRS would prefer e file, I'm just hoping to find some verification that Form 5558 e file is actually not mandatory.  The concern is would the IRS (or DOL) possibly reject a paper filed Form 5558 for a Plan Sponsor that had issued more than 10 W-2's, 1099's, etc for any given tax year.

The IRS on its website says you can file electronically or file on paper.  All of the IRS rules about counting 10 forms to get to mandatory electronic filing apply to filing payroll forms (W2s, 1099s...) and to filing a Form 5500EZ.

Here is another link https://accountably.com/irs-forms/f5558/ that does a good job talking about 5558s in plain English.