KDEconnect on 2 different networks: totally impossible?

[A. F. Cano]

Hello,

I've been trying to get KDEconnect to work across a router and it
appears to be impossible.  My internal network, where the linux KDE
is, is at 192.168.x.0, the android phone with KDEconnect is at
192.168.y.0.  Traceroute reaches the phone so it's not a routing
problem.  I have found this:

https://www.addictivetips.com/ubuntu-linux-tips/install-kde-connect-on-linux/

and it says (in the Configuring KDE Connect section):

Note: pairing WILL NOT WORK if your Android device isn’t on the same
network as your PC. Be sure that wifi is working before connecting.

I have not been able to find any instructions on configuring either the
android app or the linux end.  At the android app, if I "Add devices by
IP": 192.168.x.a it still finds "No devices".  Running kdeconnect-cli -l
on the linux machine returns "0 devices found".

The default route is set properly on the phone.  The route to
192.168.y.0 is set properly through the router at the internal network.

Is there some configuration file somewhere that I could change so that
KDEconnect works across the router? Or is this impossible?  For security
reasons I don't want wifi on the internal network.

Any help will be much appreciated.  Thanks!

Augustine