Falkon is not fully integrated in Plasma activities yet. For example, I am in the activity A and I open Falkon. Then I switch to the activity B, I click on the link "https://www.falkon.org/" (e.g., on KMail). I expect that the link is opened in a new window of Falkon in activity B. Instead, Falkon opens the links in the existing window in the activity A, and it switches back to A. This is annoying, since it "breaks" the activity separation. At the moment, I have to manually open an empty instance of Falkon in B and then click on the link. I'm using the latest version of Falkon (3.0.1) on the latest version of Plasma (15.13.2). Not sure if this should be fixed in Falkon or in Plasma, since other applications have the same problem (e.g., Kate).
It does not and will not support activities.
Any reasons for that? I don't expect a full KDE integration from other browsers, I didn't expect from QupZilla either. But since Falkon is part of the KDE project, I think that it should have that. Of course, not a priority, but why not?
Activities are not really well supported in other KDE apps either, also it have uncertain future now with switch to Wayland as it is X11 specific. And at last, I don't use it myself.
I'm guessing the problem that Falkon quits on all activites when one activity containing a Falkon window is stopped won't be fixed either?