Updated: January 8, 2018
A couple of years ago, I wrote a detailed tutorial on iPhone mount & use compatibility in Linux across multiple distributions. KDE/Plasma struggled with this the most, not seeing and/or not mounting the device automatically. But we did have a relatively neat solution in the form of idevice and ifuse utilities, with some command line hacking.
With the release of iOS 11 (and possibly one version earlier) things seem to have changed somewhat. And I have only run and tested iPhone 6 with iOS 8/9. To wit, here's another tutorial to help you work around this. At the moment, I have an iPhone 6s model for testing, and I cannot guarantee this method will work well with newer models, but overall, the procedure should be identical for the rest of the Apple smartphone range. Anyway, after me.
Tools of the trade
This guide aims specifically at Plasma use, however, we will cover all angles. It is applicable across the distro range. The only difference is in the subset of libraries and tools you will need to install. This guide has been compiled working with Kubuntu 17.10, so it works for any Ubuntu-based (and maybe even Debian) system. If you're wondering how to achieve this in other distros, like Fedora, please take a look at my guide detailing exactly this - iPhone connectivity in Fedora KDE. The principles are identical.
Let's begin with the necessary extras - the set of libraries is very similar to what we did in the past, except some tools have new, incremented versions. Nothing too dramatic:
sudo apt-get install ideviceinstaller python-imobiledevice libimobiledevice-utils libimobiledevice6 libplist3 python-plist ifuse usbmuxd
The next step is to connect your device and make sure it's recognized. You can check this with dmesg, and look for an output similar to this:
[ ] usb 2-3: new high-speed USB device number 4 using ehci-pci
[ ] usb 2-3: New USB device found, idVendor=05ac, idProduct=12a8
[ ] usb 2-3: New USB device strings: Mfr=1, Product=2 ...
[ ] usb 2-3: Product: iPhone
[ ] usb 2-3: Manufacturer: Apple Inc.
[ ] usb 2-3: SerialNumber: 42aed16e758bde7cb268 ...
[ ] ipheth 2-3:4.2: Apple iPhone USB Ethernet device attached
[ ] usbcore: registered new interface driver ipheth
Now, let's try the pair command - which is most likely going to fail:
No device found, is it plugged in?
What you need to do next is run the usbmuxd command. This is a socket daemon to multiplex connections from and to iOS devices. Normally, it should run as a background service, which we will enable later, but for now, open a separate terminal, and as sudo or root, run:
usbmuxd -f -v
The console should fill in with text, which is good. Now, in a separate console window, let's go back to trying to pair the device. As before, we will need to unlock the iPhone and trust the laptop:
SUCCESS: Paired with device 421c580dfa7ba121f591b1aed14a657bde7cb268
Now, create a mount point, something like media/iPhone. Make it accessible to everyone with chmod 777 or make your user the owner of the directory so you can access it without root permissions in the file manager. Then, mount with ifuse:
sudo mkdir /media/iPhone
sudo chown <your user>:<your group> /media/iPhone
Open the file manager (Dolphin) and navigate to the mount point.
For easier future access, you can now drag & drop the location shortcut into the sidebar, and even add a custom icon and/or name. Then, every time you mount an iPhone, you can easily go there, and if there's no device mounted, no harm done.
You can script the mount and umount procedures if you wish. Likewise, the same applies to the usbmuxd service, which you may want to be running with your system. You can enable it to run on startup - and if you get an ugly systemd error, then just "manually" start it when needed or every time the desktop logs through Plasma settings. Either one is fine.
systemctl enable usbmuxd
systemctl start usbmuxd
Other distributions and systems
To see whether it's still just Plasma having the gyp with iPhone 6s, I also tested with several other distributions, including Ubuntu 17.10, Linux Mint Sarah as well as outdated Fedora 25 Gnome, to name a few. All of these handled the device and iOS 11 without any problems. In Mint, I did have to unmount then remount the phone after making it trusted, but that's it.
There's no technical reason why Plasma should not support iPhone out of the box, given that the manual process works. And yes, there's always a possibility that Apple may change something in their devices or protocol and break it, but for now, it seems to work all right, and non-KDE desktops largely handle this seamlessly. Plasma should also join the party. The magic word is: auto-mount.
This tutorial is here to help you in the meantime. True, compiled for the Ubuntu family, but the principle is identical across the board. Get the relevant libraries, get usbmuxd, run the commands, and Bob's your uncle. If you struggle, regardless of what your desktop environment is, you should be able to achieve the desired results using the method above. I hope you find this guide useful. Stay strong.