Bug 424606

SUMMARY

I first noticed this when I upgraded my Kubuntu 18.04 installation to 20.04 (via 19.10, since this was months ago and I was not willing to wait for July as Ubuntu suggested). After the upgrade, I was unable to use KDE Connect to send files to or from the Kubuntu 20.04 PC (via the Dolphin "Send to [device] via KDE Connect" context menu option) from my Neon (User, 18.04 base) PCs. The file transfer progress meter would appear on the destination PC, but the transfer never took place. The progress meter would just stick around, showing 0% progress, until closed.

I tried the kdeconnect-cli utility too, with the same result.

Additionally, the pairings between PCs were no longer persistent. All I had to do to unpair them was to close the KDE Connect dialog or even refresh the view of KDE Connect devices on the LAN. I managed to get it to be somewhat more persistent by deleting the KDE Connect config data, but it would still discard the pairing on a reboot of the 20.04 rebased machine.

I tried booting one of my PCs using the Kubuntu 20.04 installer's live session, and while it did pair readily with my PC that had Kubuntu 20.04 installed, it had the same inability to originate or receive any files.

I chalked that up to Ubuntu having insufficiently tested the PC to PC function of KDE Connect in Kubuntu, given the heavy focus on communication with phones, and it wasn't a big bother because Kubuntu 20.04 was only there for testing anyway.

When I saw on the Neon forum that KDE had requested people try out the pre-release KDE Neon rebased to 20.04, I backed up the system and performed the upgrade. Everything went well, but I soon noticed the same behavior as before. The pairings would disappear in the same manner as before, and file transfers in either direction never happened.

I then tried the kde-connect-indicator program on the Mint (20) installation, pulling in all kinds of KDE dependencies, and once it was all installed, I saw the same behavior yet again. 

STEPS TO REPRODUCE
1. Install an Ubuntu 20.04-based distro with KDE Plasma as the DE
2. Pair it with another KDE Plasma PC over a LAN (using Samba in this case)
3. Try to use the context menu from Dolphin to send a file from one PC to another (either direction).

OBSERVED RESULT

The file transfer progress meter appears on the destination PC, but the file is never sent.


EXPECTED RESULT

The file is sent and the transfer progress meter disappears (or never appears in the first place for smaller files)

SOFTWARE/OS VERSIONS
Windows: na
macOS:  na
Linux/KDE Plasma: KDE Neon User Edition, 20.04 base or Kubuntu 20.04
(available in About System)
KDE Plasma Version: 5.19.3
KDE Frameworks Version: 5.72
Qt Version: 5.14.2

ADDITIONAL INFORMATION

It was never an issue in 18.04-based distros, but for the purposes of troubleshooting, I removed the ufw package on both ends to make sure it was not interfering. It made no difference.

I've tried wireless to wireless, wireless to ethernet, ethernet to wireless, and ethernet to ethernet. They all behaved the same way.