You can have both plans but you may run into trouble if you exceed the plan maximums. I want to ask @dmertz to comment.
As an employee, you can contribute up to $22,500 of deferred salary for 2023. If your employer also contributes (matching or not) the combined maximum for 2023 is $66,000.
As a self-employed person (sole proprietor, owner of an S-corp), you can also contribute up to $66,000 (or 25% of your net self-employment earnings, whichever is less).
https://www.irs.gov/retirement-plans/retirement-plans-for-self-employed-people
I don't think this means that if you are an employee and also self-employed, you can contribute up to $132,000. I think your overall limit is still $66,000. However, within those limits you could certainly contribute $22,500 through the full time job, and if that job doesn't have a match, you could set up a solo 401K and contribute up to $43,500 from the business, assuming the self-employment job has enough net profits to support that level of contribution.
You have to be careful with Turbotax. If you click "maximize my contribution", hopefully it is taking 25% of your self employment profits, adding them to the 401k contributions from the W-2, and checking to make sure it is under the overall limit. But that's an assumption. Turbotax may also give you suggestions based on the idea that you are preparing your taxes before April 15.
In general, it is too late to create or add any retirement funds for 2022. However, if you live in an area affected by a declared disaster (like the California snowfalls and flooding, and certain hurricanes) the deadline to make IRA contributions for 2022 may be extended. Check the IRS web site.
https://www.irs.gov/newsroom/tax-relief-in-disaster-situations
