I'm run a Fedora29 with Dolphin 18.12.2
When I connect an android device I get a notification from the mobile devices icon, and I can open a dolphin window on it if I click on "Open with file manager".
The window will show the content of mtp:/Tablet/ but the device section in dolphin's pannel area will not add the new entry (as it correctly does if I connect an external USB device)

With my older fedora version I didn't have this problem so I'm thinking that some module could be missing.
I tried installing kio_mtp and KDEconnect, but nothing changed.

If I use nautilus it shows the android entry correctly.

I hope some one will help me to correct this issue.
Thanks in advance.
Licia