Although the classic editor works, I am unable to use Gutenberg. When I disable plugins in wp-content (by changing plugins to pluginsOLD), I can edit everything just fine.
How can I restore the new editor's functionality?
You already know it's a plugin problem, so now it's time to find which is the plugin that is doing it but deactivating each plugin one by one and checking to find the one, once you find the faulty plugin you will have to:
But to be honest, normally it's better to use another plugin that does the same or code the functionality of the faulty plugin.
I also encountered the completely blank Gutenberg issue. Once you find the offending plugin and/or theme, in case it helps you trace the offending lines of code (e.g. in case you want to fix or re-implement that functionality), I'll share what I recall:
<link> tags (to pass the W3C HTML5 validator without warnings). Other JS was running fine but Gutenberg blanked out the way you describe.
In tracing an offender, be sure to have your browser's developer tools open, e.g. Chrome -> Right click + inspect. Check the Console for errors or messages that might give you better insight.