This is for Trisquel users who have Android or Apple phones. This tutorial explains how to share files between your desktop and your phone via wireless or cable without using KDE Connect. This 'magic' is called Syncthing -- a cross platform app. It is an easy and quick app to transfer your photos and everything between devices just like the proprietary software SHAREit  but with privacy and security for you. I have made similar guide before (see here) but for Trisquel 9 it is a little different so this is for you. Now let's start sharing!

Summary 

Put some photos in folder named Sync, and they will be transferred to folder with same name on phone. Do the same thing on phone, then likewise will happen to computer. Syncsynthing does it automatically via wifi or cable.

Preparations

• Install Syncthing both on Trisquel laptop and Android phone[1].
• Create a new folder named Sync on both laptop and phone.
  
• Start Syncthing on both devices[2].
• On phone, first add new device (laptop), then second, create new folder[3].
• On laptop, after two notifications appear: first add new device (phone), then second, add new folder (from phone)[4].
• Preparations done = both devices say 'up to date'.
• Jump to start sharing.
  

Start Sharing

Just like summary above:

• From laptop: put files in Sync folder.
• From phone: put files in Sync folder. 
• They will automatically transferred to each other via network used.

Explanations

Below is all the procedures to setup Sycthing on Trisquel 9:

[1] Laptop installation:

(notice that this is not syncthing-gtk package)

$ sudo apt-get install syncthing

[2] Phone installation:

First install F-Droid the play store alternative and then install Syncthing from that.

[3] Phone preparation:

1. On laptop, press Alt+F2 > type syncthing > press Enter > wait a few seconds > Abrowser appears with the web address 127.0.0.1 > Syncthing web ready to use.
2. Still on laptop, on Syncthing web, click menu > Show QR Code.
   
3. On phone, open Devices page > tap plus button > Add Device dialog appears > tap QR Code button > a scan screen appears > scan QR Code on laptop screen > your laptop detected.
4. Still on phone, type the name: Trisquel Laptop > tap check mark button > a new device "Laptop" added in Syncthing phone.
5. Still on phone, open Folders page > tap plus button > Create Folder appears > type the name: Sync > change directory path to a folder that will connect to the laptop > enable "Laptop" selection > change folder type to: Send & Receive > tap check mark button > a sync folder created.

[4] Laptop preparation:

1. Wait for a few seconds, 1st notification of a new device i.e. your phone appears > click Add button > change Device Name: Android Phone > Save > a new device "Phone" added.
2. Not too long after that, 2nd notification of a new remote folder i.e. Sync sent from your phone appears on Syncthing web > accept it > change Folder Label: Sync > change Path: /home/master/Sync by replacing master with your own username > add check mark to Monitor filesystem for changes > add check mark to Phone > Save > a sync folder "Sync" added.
3. Up to date status with green background appears like picture below. 
   
4. Now your devices are ready to share files.
   

Enjoy sharing!