Hi
I found a temporary workaround that worked. Due to the way that ABSPATH works on WordPress.com and Pressable, ABSPATH returns to a symlink that contains just the core files and no write permissions.
In this case, on the file src/llms-txt/infrastructure/file/wordpress-file-system-adapter.php, editing the function get_llms_file_path_() works:
private function get_llms_file_path(): string {
return trailingslashit(dirname(WP_CONTENT_DIR)) . 'llms.txt';
}