Please suggest solution for ready-to-use User Auth. No-Code? PHP?

I want to create an online page where users can set up an account and enter some data on a simple form.
Then they should be able to return after some time, log in, and edit the data.

I am a programmer and will manually create the form, backend code, and DB.
But I do not want to code the sign up, log in, password reset and all this auth stuff.
So I am looking for a solution where the auth is already there and I have just to add the form code. I am thinking about some alternatives:

• Is there a no-code/low-code platform that I can use? Problem with the platforms I have checked: I want to offer a free service to potentially 10m users and would have to pay for the expensive enterprise plans for my case.
• What will be an easy-to-use PHP framework that brings this stuff? I can code PHP, but am not up to date with the frameworks.
• Other suggestions?

Thanks!