Need help on backend user account management and data persistence [closed]

Question

So I'll keep it short. I have a website where my users can come and write and the strings of text are saved using their localstorage, meaning whatever text they write in that textarea stays saved on their browser's local storage.

Now this if what I'm trying to do: I wish that my users can create accounts and that text area can then be stored in their accounts on my website( that they can also access on other devices by logging in). I'm trying to go for a NoSQL solution and looking for what you guys have to recommend. I tried the following services:

Auth0: Too complex for someone like me, and doesnt do much beyond authentication.

Cloud Firestore (Firebase): Still exploring but I still can't find a way to let users store text files/tex strings in their accounts

Userbase: This if the MOST interesting one as it does exactly what I wish to do but I'm not sure if it's reliable or not. Have any of you used this service?

Literally any help would be appreciated. Thanks!