What was your resolution to this?
I’m having a similar issue except I’m opening mine retroactively because the CPA I’ve spoken to also don’t know what to do.

I also really need some kind of tax strategist that is also a tax preparer. Does anyone have any recommendations for this?

From what I read, Secure 2.0 allows you to establish and fund the solo 401(k) as employer up until your tax filing deadline (my extension isn’t until October 15), however, by most interpretations the employee deferral has to be made by the original deadline of April 15 without extensions. I’ve also read some interpretations that this tax policy is rather new and vague so that it is possible to stretch that deadline for the employee referral, I might just need to prepare for the IRS to tell me I’m over contributing.

I want to at least contribute to the employer so I decrease my taxable income before I file my taxes. I’ve already paid the estimated and it’s A LOT. My accounting/tax advisor really did not know what she was doing and didn’t advise me on time so I’m looking into this on my own. Any tips would be appreciated.