Hi, this is a variant of the plugin problem outlined in https://mail.kde.org/pipermail/kde-devel/2023-December/002234.html
TL;DR Qt6 can't load Qt5-based plugins and vice versa This also affects KIO workers. We have a number of sources of KIO worker plugins: - KIO itself provides file, http, help, ftp, remote, and trash. Since KIO is available from KF5 and KF6 we get builds of those for both Qt versions. No problem here. - kio-extras provides additional workers: sftp, mtp, smb, ... kio-extras is available for KF5 and KF6, so no problem here. - various kio-* modules, like kio-gdrive, kio-stash, kio-gopher. These should be built for both Qts, which should generally be possible, modulo some common files to be deconflicted - "Applications" that ship a KIO worker as part of their offering. Examples that come to my mind are KDE Connect that ships a kdeconnect worker and bluedevil that ships the bluetooth and obexftp workers. These project are generally not designed to be coinstallable. i.e. if I have Qt6-based KDE Connect I can't use the kdeconnect worker from a KF5 app The last case is the one giving me headaches. Possible options would be - Ignore the problem and hope nobody misses some workers in some applications - Make sure all (relevant) workers are available for both Qts, adding some complexity to the build, release, and packaging process - Since KIO workers run out of process it should be technically feasible to come up with a way to run KF5-based worker plugins from a KF6-based app and vice versa. I have not tried to implement that though, and it would require some non-trivial surgery on KIO internals