KDE Connects works amazingly for me. I get, once in a bluee moon, the random "Can't see the other device" bug. I have solved it with the basic dis/connect to the wifi both on my phone and computer. Also, check your Firewall on your computer. Some distros will not "Auto add" KDE Connect to the exception list of your Firewall. Some routers also put LAN and WLAN devices on different VLANS.