I'm a consultant who received income from a company based in Switzerland last year. Are they required to provide me with a 1099-NEC?

No, they do not have to follow American tax laws.

I am also a consultant that received income from a European based company that did not provide an NEC form. Where do I enter the income ?

If you did not work as an employee and did not receive a Form W-2, you are likely a self -employed taxpayer.  If you worked as an independent contractor and did not receive a Form 1099, you will enter your information on a schedule C.  Due to it's international based company, you might not receive a Form 1099-NEC. To enter your self employed income without a 1099, here are the steps:

In TurboTax online, 

• Sign into your account, select Pick up where you left off
• From the upper right menu, select Search and type in schedule c and Enter
• Select the Jump to schedule c
• Follow prompts 

As a self-employed person, you’ll need file a Schedule C to report your income and expenses.  You also need to pay self-employment Social Security and Medicare taxes by filing Schedule SE with your tax return.  The rate is 15.3% of your self-employment earnings.  But you also get to deduct half of those taxes on your 1040 as an adjustment to income. Most taxpayers with self-employment income make quarterly estimated tax payments based on the amount of income the business earns.  To see what you can deduct, click here: Deductions