To be fair, the max you can put into a solo 401k on the employer side is limited to 20% of your net annual profit (business income minus half of self-employment tax). So in order to put in $30,000, you need to have net income of around $160k, which is doable, but more than a little contracting.

For most people here, the mega backdoor Roth is probably more doable, assuming your employer offers the option.