Does Android have a built-in FTP client? Does Android have a built-in FTP client? Even a basic one, like ones that are built into PC browsers and file managers? I know there are good free apps with FTP clients (like Ghost Commander), but I'd like to know if there's a way that doesn't require app installation. I'm excluding chrome's FTP support, since that is being deprecated, and not all android phones have chrome built-in.
No, for better or worse, Android does not have an integrated FTP client.
As you've discovered, many third-party apps are available to fill this gap.  Some of them are dedicated FTP clients, while others are integrated into file manager apps.