By deleting this here, we can just reuse what the overridden block is already doing, but with escape():

import { escape } from './utils';

export default function save( { attributes } ) {
	return (
		<pre>
			<code>{ escape( attributes.content ) }</code>
		</pre>
	);
}

Actually, removing this is causing problems. In WordPress 5.4.1 without Gutenberg active, I'm getting an error where the save function in the blockType is undefined:

For some reason settings.save is defined up front, after being filtered it gets dropped, even though all of settings is being returned:

Perhaps it is due to this apparent race condition I commented about on the subsequent lines:

In any case, capturing the original save the first time we see it seems to fix this:

--- a/src/index.js
+++ b/src/index.js
@@ -26,6 +26,8 @@ import * as BlockEditor from '@wordpress/block-editor';
  */
 import languagesNames from './language-names';
 
+let save;
+
 /**
  * Extend code block with syntax highlighting.
  *
@@ -37,6 +39,14 @@ const extendCodeBlockWithSyntaxHighlighting = (settings) => {
 		return settings;
 	}
 
+	if (settings.save) {
+		save = settings.save;
+	}
+
+	if (!save) {
+		return settings;
+	}
+
 	const useLightBlockWrapper =
 		settings.supports &&
 		settings.supports.lightBlockWrapper &&
@@ -269,6 +279,8 @@ const extendCodeBlockWithSyntaxHighlighting = (settings) => {
 			);
 		},
 
+		save,
+
 		deprecated: [
 			...(settings.deprecated || []),
 			{

But this hardly seems like the right solution.

@youknowriad Do you know what's going on here?

I think that filter might run for deprecations too. So it's possible that one of them don't have save.