+++ This bug was initially created as a clone of Bug #398934 +++

SUMMARY
Can't connect phone to desktop PC with KDEconnect

STEPS TO REPRODUCE
1. I have   KDEconnect v1.3.3 up and running on the desktop PC
2. I have installed Android KDEconnect v1.19.1 from Google Play store on Android
Both devices are connected to the same router, both have 192.168.11.* IPs.
Android has a working wireless connection to the router.
Ubuntu has a working wired ethernet connection to the router.
I can ping the Android device from Ubuntu, and can copy files in both directions using app Wifi File Transger
The router is running DD-WRT, Firmware: DD-WRT v3.0-r41057 std (09/18/19)

OBSERVED RESULT
Neither device's KDEconnect application can see the other device.
Entering the Ubuntu IP address into Android's KDEconnect app doesn't help

EXPECTED RESULT
I would expect KDEconnect on each device to list the other device by IP or name

SOFTWARE/OS VERSIONS
Ubuntu 18.04.6
Motorola Moto X Style XT1575 / Android 7.0 Nougat

ADDITIONAL INFORMATION

*** Cloned from bug follows ***

SUMMARY


STEPS TO REPRODUCE
1. I have KDE up and running on the desktop PC.  kdeconnect v1.3.1
2. I have installed Android KDEconnect from Google.
On the Android (Samsung Galaxy Note 3 Neo) the desktop is offered for connection.
Both devices are connected to the same router, both have 192.168.2.* IPs.
Android has a working wireless connection to the router.
Debian has a working ethernet connection to the router.
The router is running DD-WRT.

EXPECTED RESULT
I do not know what a successful connection looks like.
Hopefully I would be able to recognize it.

ACTUAL RESULT
When trying to pair, Android says, "Abbruch durch Gegenstelle" (interrupted by peer).
In the desktop /var/log/syslog I find: "Peer 192.168.2.24:nnnnn is not from a LAN" (many times),
where nnnnn is the varying port number.

SOFTWARE VERSIONS
KDE Plasma Version: 5.13.5
KDE Frameworks Version: 5.49.0
Qt Version: 5.11.1

ADDITIONAL INFORMATION
Maybe a specific setting in the router could help?!