Same here, pressed CTRL+ft about 5 times ‘et voila’ Gutenberg works as it should do.
Evgeny, you commented on me using Evolve and not Evolve plus. I tried upgrading to ‘Plus’ on my present site and as a result I lost all the Additional css and my front page went all haywire so I reverted back to Evolve not Plus. Still good enough for this particular site.
After having disabled all plugins, cleared the cache (CTRL+f5) and ensured my php version is 7.3 the problem still persists. Changing the theme to 2020 allows the Gutenberg editor to work as it should.
For what its worth, I too have severe problems since upgrading to WP 5.6 in as much as I cannot use the Gutenberg sditor, its just a white page with the following error report:
The editor has encountered an unexpected error.
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