No way for us to know from here, as we don't have access to your network.
You'd have to take stock of all your connected devices, identify their MAC IDs and IP addresses, and compare them to the unknown devices.
The above devices just showed up on my iphone as connected to my XFI home network. What are they and should I work to delete them?
Any chance you have a Dell Inspiron 7773?
And do you have any Espreesif WiFi IoT / Smart Home / Smart Plug devices ?
The only puzzle is why the notification said this was the first time it connected since I've used it on my network for years.
It's likely because your gateway device had just recently received the firmware update that contains the advanced security app.
Dead thread from last year now being closed.