That caused my WordPress plugin Crayon Syntax Highlighter to fail. Some googling suggests php-7.3 switched to pcre2, which is more restrictive in terms of escaping special characters.

Luckily, this is very easy to fix. Edit crayon-syntax-highlighter/crayon_langs.class.php, look for preg_match. Any patterns in that function containing the dash character (-) now needs to be escaped with a bashslash (\).