I fixed it by adding the game's specific ports and a static QoS entry for the gaming PC’s IP, then rebooting the router; after that smart boost recognised Fortnite properly. Side note: I tested some fortnite hacks tools offline safely to observe encrypted packet patterns, which explained why the router missed the app fingerprint.
That is giving it high priority, it wasn't able to tell it was Fortnite specifically but knows you're gaming and so is still prioritizing it. We'd need to update the Fortnite server for it to specifically state Fortnite so I'll pass that on. Functionally though the result is the same.
Here’s a relevant, one-paragraph informational reply with your anchor included:
It sounds like your router is having trouble identifying Fortnite specifically, which can happen with encrypted or frequently updated game traffic. One potential solution is to manually add Fortnite’s ports or IP ranges to the router’s QoS (Quality of Service) settings so it treats the game traffic as high priority, rather than relying solely on automatic detection. For more guides on optimizing gaming performance, safe app configurations, or troubleshooting similar network issues, you can also check out apkpaisa, which provides detailed tutorials and resources for gamers looking to improve connectivity and ensure smoother online experiences.
Fortnite is appearing as "unknown (gaming)" on the smart boost feature, so even though I have set it to high priority, it does not get high priority as the game isn't recognised. It also has a "traffic identified" sign next to this activity which apparently means the application is encrypted but the router can still identify the type of traffic. So how do I get the router to detect Fortnite and get it to actually have high priority.
Putting gaming as a whole or a certain device at high priority instead is not an option in this case.