New windows are pop-under

I am using Firefox 107.0 from a package on Kubunto 20.04 with KDE Plasma 15.8.8 . Whenever I open a new FF window, it pops under. This is annoying since I have to dig for it. I think the behaviour should be to create a new window on top. Any idea how to change that behaviour?
N.B. in the preferences under Browser privicy there is a selectbox to block or unblock pop-up windows, but that is a different thing and that setting does not change the behaviour.

When you are saying “open a new FF window”, do you literally mean a new “floating window” (popup) or is it a new tab in the current browser-window?
Can you point us to somewhere we can try ourselves to be sure what you are talking about?

Hi Stig, thanx for your reply. I try to avoid tabs whenever possible. The fact is, when I open a new window in FireFox (from drop-down with RMB on the already open FF icon in the menu bar at the bottom), no new window is opened, so it does not actually pop-under. Instead I just get a new entry in the list of FF windows (LMB on the open FF icon in the menu bar at the bottom). So I have to go there and select the new window to see it. It makes more sense to me that if one selects “New window” a new window is actually opened on top, but I cannot find how to force that behaviour.

Hi Tom

I still don’t fully understand. But I have concluded you are NOT talking about for example shift-clicking links on some webpage to open link in new window.

You are talking something about browser and Kubuntu UI/options, and probably mostly about Kubuntu (“FF icon in the menu bar at the bottom” is referring to a Kubuntu menu-bar I assume?), which I don’t know anything about.

But if you from Firefox’s “burger-menu” choose “New Window” (or simply press ctrl-N), then it will open a new window on top as expected.

Might need someone with Kubuntu knowledge to help you further. Have you tried asking in a Kubuntu-related forum?

Stig, I cannot make a screenshot of expanded menus, but I’ll see if I can attach the cut-out of the Firefox button in the standard bottom desktop menu bar that I am talking about. Using the hamburger menu in an open FF window to open a new window has the same behaviour: a new entry in the list of open FF windows, but the new window is not actually opened. I don’t know if this is a KDE/Plasma feature: this behaviour is peculiar to FF, other applications do open new windows. In any case I don’t know where it is coming from or whom to ask.

I appear not to be able to attach files or pictures here?