TL;DR: Facebook Connect will stop on February 11, 2024 and Google Sign-In later in 2024.

What is OAuth?

I'll be using "OAuth" term a lot, so here's the definition from Wikipedia:

OAuth or Open Authorization is an open standard for access delegation, commonly used as a way for internet users to grant websites or applications access to their information on other websites but without giving them the passwords. This mechanism is used by companies such as Amazon, Google, Facebook, Microsoft, and Twitter to permit users to share information about their accounts with third-party applications or websites.

Informations

In mid-October I received an email from Facebook telling me that the application used for Facebook Connect must be linked to a Meta Business account otherwise on February 11, 2024 Facebook will stop the app.
I can't create Meta Business account because I'm not a company.
As I've only saved the ID given by Facebook, I have no other way of identifying a user.
So, to avoid losing access to your account, you need to set a password, like that you can log in with classic username/password instead of Facebook Connect.
You can also set your email, it's only used for forgotten password requests.

Q&A

Why didn't you save the email the OAuth sent you?
Based on the GDPR, I only saved what is mandatory to identify an user. To do this, I used the OAuth identifier (sometimes unique for each application) and that's all i needed to link a blueprintUE account and an OAuth account. Also, not all OAuth systems send the email, sometimes you need an elevation access to get this information.

Why don't you create a new Facebook application?
This is not possible because Facebook generates a unique identifier for each application and for each user, so creating a new application will only work for new users.

Why don't you update Facebook application type to avoid Meta Business Account?
It's not possible to change that.

Why remove Google Sign-In?
Because I can no longer trust third parties, the Internet has changed and I don't know when Google will change its policy.

How can I keep access to my account?
First log in with Facebook Connect or Google Sign-In, then go to your profile edit page, after scrolling a little you will see the "Change password" form. Here you can set your password to log in without using OAuth, but with a classic username/password.

How to log in after February 11, 2024?
Click on the log in button or on this link: https://blueprintue.com/#popin-login then you need to fill your username and password.

How do I reset my password?
First you need to add your email in the profile edition page otherwise no email will be sent. Then you can use that form: https://blueprintue.com/#popin-forgot_password to reset your password and follow the next steps.