Yes! For landlines, It just depends on what phone carrier they have. If they have a supported carrier, you can help them get protected!
If you're setting it up for a friend or relative that doesn't have a computer, you can use your own Nomorobo account. Just add their phone number to your account, and it will give you the setup instructions.
For mobile phones, simply download the Nomorobo App on their device and follow the setup instructions.