As others have stated, my suggestion would be forking Classic Editor and thereby securing its future. Enhance it and focus on providing a well maintained alternative to Gutenberg.

I’m sure I speak for many others when I say this: The number one reason I don’t use Gutenberg for client sites is 90% my clients don’t want a page/theme builder. They come us to design/maintain a site for them and they simply want to update the content in the easiest possible way.

If the Classic Editor dies it will be the end of my road with WP.