KDE Connect 1.4.0 Fails To Connect To Older Phones

[rubencito]

New install of 20.04 to new computer (2-in-1 laptop).

Connected to network with several old computers (2004 to 2010 vintage), several old tablets (running Android 5 Lollypop) and one old phone (Samsung II running Android 4.1 Jelly Bean).

Computers running diverse old Linux distros (from Wary Puppy 5.5 to Kubuntu 16.04, passing through Arch, Slackware, Lubuntu, etc.).

KDE Connect works like a charm for all old devices. I don't even remember how I managed to make it work for all, but it was vital to use a very old version of it on the phones (1.8.4 aka 1841 --imo the best version of the program).

Version on the old PCs is 1.0.3

KDE 1.4.0 in the shining new computer cannot see the old versions installed. Not on the PCs, not on the phone, not on the tablets.

Is there any way to configure it to make it compatible with the old software?

Failing that, is there any way to install an old version of it in this computer with Focal Fossa?

Thank you.

[Fred47]

I don't think you can run mismatched versions of KDE Connect. It is compatible with Android 4 and newer.

[rubencito]

I found the solution!

It seems phones and tablets with older versions of Android (< 6.0) use transport layer security (TLS) version 1.1. KDE Connect 1.4.0 (and above) requires TLS 1.2.

The way to make a newer version of KDE Connect "talk" to older versions is to disable the requirement for openssl to use the 1.2 TLS protocol (reduce the security, but that's no big issue if you have everything firewalled and obscured in your local network, behind a router).

So we need to set the default security level back to 1, using

CipherString = DEFAULT:@SECLEVEL=1

The elegant solution with all the proper checks and set to work at start up was provided by slowpeek here (thank you!) :

https://github.com/slowpeek/kdeconnect-focal-ciphers