End-of-life for the classic editor by the end of 2021

[jeanfredrik]

Gutenberg is set to finally supersede the classic editor by the end of 2021 when the classic editor will no longer be supported. https://make.wordpress.org/core/2018/11/07/classic-editor-plugin-support-window/

What’s the plan going forward? How do we need to prepare for this change? I can see that it affects Modularity, but also other features and panels related to the editor, like the Lix calculator.