Edit: The first thing I did was connect my phone to a wifi PC with a USB cable.
So mtp appears to be working in Lx 3. I plugged in my smartphone and first got:
Then I went to SystemSettings>Hardware>KDE Connect:
If you don’t see your phone listed then go to the link for “KDE Connect Community wiki” and follow the instructions for Firewalld.
And of course you should have already installed the KDE Connect app on your smartphone as it tells on page in SystemSettings. Result:
More results:
If the old fart @ben79 can do this all you young folks should be able to do it…
Edit: This is a fairly old install of Lx 3.03 with testing repos enabled. System was updated on Wednesday 02/14/2018.
Edit again: I don’t think having testing repos affects this at all. It should work just fine on a machine with standard repos only.
Thank you Ben for the “young” although I’m afraid I don’t deserve it since a couple of ten years ago!
This seems to be a long post by now. Not to extend it unnecessarily, the point that remains is that you Ben wouldn’t do anything if your PC wasn’t wifi connected and you could not use KDE connect. The old Lx 3.0 had “full” MTP support (via kio-mtp?), then you could just click on the icon “Samsung Galaxy models(MTP)” and Dolphin would open allowing you to browse, copy and paste, your cell phone contents without a wifi network.
Ben, if you have a LX 3.03 installation, and you can browse your cell phone content with a usb cable without a wifi network and kde-connect, then I have something wrong here to correct for.
Yes I can definitely connect with a USB cable and browse content on my phone without KDE Connect.
Now I have KDE Connect “Unpaired” or disconnected. That is what the very first screen-shot is. Here is a photo that I know is only on my phone:
Just using a USB cable and Dolphin and Gwenview.
Also I checked on the same PC in a partition without testing repos enabled and it does all work the same.
Ok. I can do the same if I choose PTP protocol to browse the cell phone camera content. However, this restricts the access to the cell phone only to the camera directory. Other directories like whatsapp are not accessible unless I could try the MTP protocol or using KDE connect with wifi. The way the cell phone “communicates” with the computer is set on the cell phone where I can choose among a simple charging connection, a media transfer connection (MTP) and a camera connection (PTP).
Here I have a fresh install of LX 3.02 updated to 3.03 with all updates up to now.
Without wifi if I plug my cell phone with a usb cable and choose MTP protocol I see this,
You can see in right lower corner the device notifier telling about the availability of my cell phone for browsing with dolphin. But if I click on the cell phone icon, instead of opening it as it used to do in the near past, now I get the following error pop up window,
It tells “file or folder … doesn’t exist”.
If I choose the PTP protocol I see this,
Then, in this case I have the option to transfer photos using Gwenview or digikam and to open with Dolphin but only the camera stuff. Can’t do anything with other directories.
The more I look at this it seems you are right in that mtp isn’t working as it should. But I also don’t understand this issue all that well at this point in time…
If I understand correctly we have determined that kio-mtp is not working and it is dead and not to be used any longer. So, maybe, that means something is wrong with kio-extras? Or maybe I’m just lost on this issue. 
I like being referred to as young ,but I’m 60 
is that a print shop ?
I like guitars too, they make us look young I guess … I’m 60 now and still growing …
Yes, I have uninstall kio-mtp and everything looks the same. It seems that, if not removed, the support to MTP protocol in KDE now is provided by something else, maybe kio-extras only …
The link for reddit KDE above reports that with a patch to kio-extras, MTP support is OK.
Keep on Rock’n …got a gibson les paul ?
I don’t. Now, I’m more of a listener than a player.