Announcement from the Proton team on Reddit (Libreddit link):

Today, we’re increasing file storage limits on the free plan.

Instead of sharing 1 GB between files and email, you’ll now have:

5 GB for Proton Drive

1 GB for Proton Mail

Additional context: For Proton Drive, you now start with 2 GB and for Proton Mail, you start with 500 MB. After signing up for the Free plan, you can unlock the maximum storage allowance on each service thus:

You can boost your Proton Mail storage from 500 MB to 1 GB by completing four account setup actions.

You can boost your Proton Drive storage from the default 2 GB to 5 GB by completing three tasks.