Remove Inline Styles From Pasted Content on Save

// Leave administrators' content untouched.
$wpide_clean_skip_admins = false;
// Post types to clean.
$wpide_clean_post_types = array( 'post', 'page' );

add_filter( 'wp_insert_post_data', function ( $data ) use ( $wpide_clean_skip_admins, $wpide_clean_post_types ) {
    if ( ! in_array( $data['post_type'], $wpide_clean_post_types, true ) || ( $wpide_clean_skip_admins && current_user_can( 'manage_options' ) ) ) {
        return $data;
    }

    $content = wp_unslash( $data['post_content'] );

    // Process only the HTML between block comments, so block attributes stay valid.
    $parts = preg_split( '/(<!--.*?-->)/s', $content, -1, PREG_SPLIT_DELIM_CAPTURE );
    $depth = 0;
    foreach ( $parts as $i => $part ) {
        if ( 0 === strpos( $part, '<!--' ) ) {
            if ( preg_match( '/^<!--\s+wp:[^\s]+\s+\{.*"style"/s', $part ) ) {
                $depth++; // Styled block: keep its markup as is.
            } elseif ( $depth && preg_match( '/^<!--\s+\/wp:/', $part ) ) {
                $depth--;
            }
            continue;
        }
        if ( $depth ) {
            continue;
        }
        // Keep only text alignment, which the classic editor stores as an inline style.
        $part = preg_replace_callback( '/\sstyle=("|\')([^"\']*)\1/i', function ( $m ) {
            return preg_match( '/text-align\s*:\s*(left|right|center|justify)/i', $m[2], $align ) ? ' style="text-align:' . strtolower( $align[1] ) . '"' : '';
        }, $part );
        $part = preg_replace( '/\sclass=("|\')\s*Mso[^"\']*\1/i', '', $part );
        $part = preg_replace( '#</?font[^>]*>#i', '', $part );
        $part = preg_replace( '#<span>(.*?)</span>#is', '$1', $part );
        $parts[ $i ] = $part;
    }

    $data['post_content'] = wp_slash( implode( '', $parts ) );
    return $data;
}, 20 );