I can see that Ferdinand already pointed you to the article for Windows Backup, so there's no other information on that to add here. However, I've also read your reply, and as someone who use a gmail account for Windows Backup, I'd like to share some clarifications over this situation so you better know what to do next!
Now, what you quoted is correct, but the wording might have created some confusions: using gmail as email provider is not the issue. What matter is to use that gmail account to make a "personal Microsoft account (MSA)". That MSA belong to the "and so forth" part in your quote. It's Work or school Microsoft accounts that won't work.
So basically, like me, after creating a MSA with your gmail alias, you can use it to sign into Windows and turn on Windows Backup like the instructions already shared above. Yes, it's still a Microsoft account, but it's using your *gmail.com entry (there's no need for *@outlook.com or *@live.com, if that was what you're concerned about).
If you have other questions on this, feel free to ask! I'm also use a gmail-based account so it might be helpful with your situation!
If you think the answer is helpful to you, please mark this as accepted. If you have extra questions about this answer, feel free to click "Add Comment" and ask!
Note: Follow the steps in our documentation if you want to enable and receive the related email notifications for this thread.