Unfortunately I have completely forgotten how I've logged onto D&D Beyond.

As a result I have invested cash into a platform I cannot access from other platforms, only my mobile phone.

How can I discover my login method and be able to use D&D Beyond with my laptop?

There are only a few choices, and some are brand new. You can either log in with Google Authentication, Twitch login, Apple ID, or Discord.

Go to My Account from your phone and it should tell you there. The one with the green chain symbol is the one you are logged in with.

I didn't know that page existed and I definitively couldn't navigate to a page like it - despite my best efforts.

Thank you.