I would not rely on a single signal. I would score it across layers.
Structured signals - franchise directories, FDD references, NAICS patterns tied to franchise models.
Website signals - franchise pages, language around territories, franchise fees, royalties.
Negative filters - dealer networks, affiliate programs, corporate owned multi location chains.
Then assign a confidence score instead of a binary tag. Set a threshold for routing.
This keeps precision high and reduces false positives.