It is surprising how difficult most camera companies have made it to avoid their subscription services.

Multiple companies that used to offer local rstp streaming have summarily removed support in firmware upgrades without notifying their customers. Even companies that support it (like Foscam) demand developer agreements be signed to get basic camera command information. Tp-link supports rstp but requires an phone app and Internet connection to configure their cameras.

Like you, I will never connect my cameras to the Internet, but we are slowly approaching a time when that by itself will be a cause for police investigation.