Are you talking about the root directory ("/") or a writable location like the sdcard on your phone? It is expected that you don't have write access to files that you don't have access normally on your phone.

(In reply to Albert Vaca from comment #1)
> Are you talking about the root directory ("/") or a writable location like
> the sdcard on your phone? It is expected that you don't have write access to
> files that you don't have access normally on your phone.

I'm talking about the sdcard/storage location (e.g. /sdcard/emulated/0), which I have write access to on my phone.

Can confirm that all files appear as owned by root in the connected KDE system:

Terminal emulator in Phone:
u0_a145@g3:/storage/external_SD/Android/data/net.osmand/files/tracks $ ls -l
-rwxrwx--- u0_a155  sdcard_r     2130 2016-09-10 22:59 circuit de lesquillon.gpx
drwxrwx--- u0_a155  sdcard_r          2017-05-05 16:14 rec
-rwxrwx--- u0_a155  sdcard_r      743 2017-05-05 15:04 test.gpx
u0_a145@g3:/storage/external_SD/Android/data/net.osmand/files/tracks $

Shell in connected KDE system:
dani@setna:~/.config/kdeconnect/60ca260263df1100/kdeconnect_sftp/60ca260263df1100/storage/external_SD/Android/data/net.osmand/files/tracks
$ ls -l
total 8
-rw------- 1 root root 2130 sep 10  2016 circuit de lesquillon.gpx
drwx------ 1 root root    0 may  5 16:14 rec
-rw------- 1 root root  743 may  5 15:04 test.gpx

Same issue here, LG G3 (d855) running latest LineageOS, full permissions granted to the app, and with on the other side a PC with an updated Neon user (the same issue occurs with Kubuntu 16.04 on another laptop).

In my case, the files/dirs in the SDcard are listed as not writable, and even as root I can not write any change to that FS:

> vale@Gatsu:~/.config/kdeconnect/fba3e36ee035c1b4/kdeconnect_sftp/fba3e36ee035c1b4/storage/5255-1406
> 23:46-$ la
> total 1.4G
> -r-------- 1 root root 547K Mar 29 12:24 addonsu-arm-signed.zip

On the other hand, the contents of the phone's internal storage are listed as writable, and are writable as normal user even if listed as being root-owned:

> vale@Gatsu:~/.config/kdeconnect/fba3e36ee035c1b4/kdeconnect_sftp/fba3e36ee035c1b4/storage/emulated/0
> 23:47-$ ls -la
> total 8
> drwx------ 1 root root  0 Jan 14  1970 Alarms
> drwx------ 1 root root  0 Apr 12 09:44 Android

I have this relevant line from mount:

kdeconnect@192.168.1.8:/ on /home/vale/.config/kdeconnect/fba3e36ee035c1b4/kdeconnect_sftp/fba3e36ee035c1b4 type fuse.sshfs (rw,nosuid,nodev,relatime,user_id=1000,group_id=1000)

This problem was fixed by commit: 0b3f0acde52d66bc86d50f2c8b215b78e5e127be