Up to Desktop Fresh R5, we used to release lightweight editions on the basis of LXDE. However, LXDE is based on GTK+2 library stack which didn't get significant updates since the year 2011 - all new features are now implemented in the GTK+3 series. However, migration from GTK+2 to GTK+3 is not smooth and some developers are not happy with the ew stack. In particular, after experiments with GTK+3 many LXDE developers decided to consider Qt as an alternative and in the year 2013 they decided to merge with Razor-qt project and create a new Qt-based lightweight desktop environment named LXQt.
The old GTK+2-based LXDE is not dead and is still developed by a group of volunteers, but their progress is not as significant as LXQt's one. In particular, there was almost no significant difference in LXDE components between LXDE editions of ROSA Desktop Fresh R4 and Fresh R5. But our distribution has a "Fresh" word in its name, so we decided to give a chance to a new desktop environment. And starting from ROSA Desktop Fresh R6, we provide an ISO image based on LXQt.
You can install LXQt environment in any ROSA Desktop Fresh variation (starting from R4) by installing task-lxqt package.
LXQt is built with Qt5 framework and the Desktop Fresh LXQt edition tends to include applications that also use Qt5, in particular:
However, we couldn't find Qt5 programs for all possible use cases, so our ROSA Desktop Fresh LXQt edition still provides several Gtk applications. The most noticeable ones are LibreOffice and Firefox - we decided that it would not be a good idea to provide semi-functional analogues even if they are based on Qt5 (though volunteers are welcome to test otter-browser from our repositories which is based on Qt5 and tries to mimic Opera 12.x GUI).
It is worth noting that LXQt has its own Control Center and ROSA-specific configuration tools such as "Install and Remove Programs" are smoothly integrated into it.
ROSA Desktop Fresh LXQt uses SDDM desktop manager which is a recommended DM for Plasma 5, so it is likely that you will see it in futre KDE-based ROSA releases.