If you're building a custom theme for your clients, it's a good idea to install old version of Gutenberg plugin so you don't have to fix the theme to update to WP 5.3.

You can download old version of Gutenberg from here https://wordpress.org/plugins/gutenberg/advanced/

The version we're using now is 5.4.0 but I recommend going to 5.6.1 because it has very useful Group block.