Hi everyone! Thanks for reading this! And yes, this problem has a workaround.
I have just reinstalled Windows 10 1909. When I entered my MS account (my email), I was asked to select one of 3 numbers in my iOS MS Authenticator app. I also set my fingerprint and face authentication. Everything run smoothly.
Later on, I have tried to access a folder on this computer from another one. However much I tried, I was unable to access. I checked Event Viewer Security log and it was clearly stated there "wrong user or password". Strange.
As I was sure I knew my username/password, I did one last thing: I used recovery options and rebooted into "Command Prompt" Mode. Voilà! It did not recognize my password.
To fix this, I changed my login to use a local account instead of MS account. I was asked for a username (which I select the same 5-letter one) and the same password of my MS account. Problem solved.
To bring things back to what it was before, I returned the login to use my MS account.
I would like to have someone to validate my workaround and perhaps to have someone inside MS empowered to fix this to solve it. It is really tricky!
Thanks for your attention!