I have a scenario where I need a user with a generic mobile device (no custom apps installed) to be able to retrieve a PDF off of a BLE- and NFC-enabled device (nRF5340) running Zephyr RTOS, in an offline environment (no ability to open an internet URL, no ability to download an app). The use case is allowing people to download a technical user manual off of a device in a remote setting with no phone or internet service.
The trickiest part is finding a tool that Android/iOS devices support natively. With a custom app this would be easy, as I could transfer the file over BLE and save it on the device, but that is not an option here.
My current line of thinking is around using a HTTP Proxy GATT service on the nRF5340, and allow the mobile phone to make an HTTP request over the BLE connection. The GATT service would then proxy the request to itself, i.e. an HTTP server running on the nRF5340. This requires running a TCP/IP stack on the nRF5340, but that's fine and Zephyr supports it.
My question, specifically, is around whether Android/iOS would natively support using an HTTP Proxy GATT service on a connected BLE device. I'm quite experienced on the Zephyr/embedded side, but not so much with mobile development.
I realize that this is quite a generic question, but it's generic because I need some community guidance on how to focus it (i.e. selecting the right tool/technology to focus on). If there's a much better approach that I'm not considering here, I would very much like to hear suggestions.