Of course if you make a solo 401(k) contribution you would be an active participant in a workplace retirement plan.
Just because a traditional IRA contribution is not deductible does not necessarily mean that making such a contribution would not be beneficial. Depending on how much you have in traditional IRAs, it might make sense to to a Roth conversion after making a nondeductible traditional IRA contribution. Remember, the pre-tax retirement contributions are deferred income. You (or your heirs) will eventually pay taxes on the the pre-tax money (assuming that it does not decline in value due to investment losses).
