how to download apps without payment method

Incorrect!

Please view these articles:

Create or use your Apple ID without a payment method: https://support.apple.com/en-ca/HT204034

Change or remove your Apple ID payment information: https://support.apple.com/en-ca/HT201266

Why can’t I select None when I edit my Apple ID payment information? - Apple Support: https://support.apple.com/en-gb/HT203905

Buy an iTunes gift card and redeem.

Don't be too sure of yourself.

Even some payment methods are not accepted.

It depends in which countries you are doing it.