Unity Learn JR programmer issues.

It shows a circular loading progress bar and then the whole screen just becomes white when trying to access

Unit 2 - Basic Gameplay - Unity Learn.

This is happening to multiple users, across multiple browsers and on mobile.

This does not appear to be just you. Checking the errors, one has to do with react, which is a js library dealing with displaying components on screen, so that may be the issue. This is likely a problem you will have to wait for unity to fix. If you need other resources in the meantime, youtube is a great resource for learning Unity.