https://xkcd.com/1683/

Yes

I think the correct tool for my purpose would be something like Popup window, if you care about that part.

SSB is still around, but also not what I was looking for. I just wanted a frameless window (and no other pwa functionality).
Fullscreen I disabled using my window manager. Under Linux you can commonly use alt+F3 to bring up the “right click on titlebar” menu, then disable fullscreen there. Generally ever window manager can disable fullscreen for windows, in a more or less accessible way (cough ms windows dll calls cough).

As mentioned below, This is recovery. I could ban kiosk mode to a separate profile, but unless you invent a time machine this won’t undo having opened kiosk mode in an in-use profile.

Yes, this is more of a recovery operation. Whatever the fix may be, modifying the browser itself to open a window without decorations would be easier.

There are some usecases in which you really don’t want to restart your browser.
The easiest way to update your kernel is to restart your pc, yet there is a market for live-patch kernels.
If someone accidentally infects their instance with kiosk, it may occasionally be preferable for them to follow a complex procedure to recover the instance, rather than doing the “simple” thing of restarting it.

Restarting may solve many problems, but there is a more difficult but less invasive solution almost every time.
Much like reinstalling may solve even more problems, but you can see that doing a reinstallation is not usually the right course of action.

Kiosk mode doesn’t just force fullscreen, it disables right click, the tab and title bar, …
Basically the browser is close to unusable until kiosk mode is ended, which I currently only know how to do via restarting Firefox.
And F11 is also disabled by kiosk mode. Interestingly, on the windows that were started before kiosk mode, it puts them into proper kiosk mode (after which F11 stops working of course).

And a grandmaster at that! Has such unpresidented talent ever been seen on this world?

Shoutout to boost at this point for still not supporting spoilers btw. /s
@[email protected] if you needed a reason, observe

Nice

OpenSUSE 42.3 standing tall

Yes, I just updated the post, you can see the process in my various comments.
It seems to be caused by uBlock origin, though I haven’t yet investigated deeper. It might be the combination of the firefox version and the ubo version, and it may be dependent on a specific setting within ubo, I don’t know yet.

Do you have ubo installed? If not, could you try installing it and see if you can recreate it then? Specifically version 1.54.0. You’ll have to find a new test page or clear cache after ubo has been enabled.

Actually it happens on the forked profile too now, restarting ff did not clear the cache there and it only occurs on newly opened pages now, so what I assume happened was I initially tested while ubo was not yet updated, since the laptop has been sleeping for a while. The browser generated a bunch of cache entries for my test pages and those continued working when ff updated ubo. Clearing the cache now has it break on all pages and fix itself when ubo is disabled like on the other device.
Therefore this seems like a clear ubo issue, independent of platform and other factors. All 3 affected profiles have similar ubo config, so I’ll investigate that now. However it is not a firefox issue, I will move the issue elsewhere.

I have Pinned it on uBlock Origin.
ubo seems to prevent creation of cache for pages while it is active.
Testing around with enabling and disabling addons, I saw the issue disappear. I then reenabled all addons and the issue was still gone. So I restarted and it came back. Then I disabled one after another, and got to it being ubo. I then tried disabling it, loading a “gallery page” and an entry on it, then reenabling ubo. The pages were still cached, but visiting a different entry would reload that one every time. Same for any other newly opened “gallery” and “entry” pages.
This explains why this didn’t happen in the test profile, which has no addons installed, but the mirrored profile on the laptop does have ubo and ff on the same version, however I do not observe the behavior there. I will investigate further.

I have now found instances it doesn’t happen for. It might be related to the number of open tabs, or some other indicator of recent heavy usage.

I have now tried this behavior on more profiles and devices (originally I tested on 2 profiles), and it it seems this behavior isn’t universal. On the same device (gentoo linux) and a laptop (windows 10) I do not see this behavior. One profile (my main profile) has many historic changes, the other though is quite new and not very unconventional settings wise. Both see this issue. The third profile on the same device is basically empty, only used for testing a few times.
However the win10 profile is a fork of my main profile from 1.5y ago, and should thus be similar in usage and configuration weirdness, yet it works just fine. The only Idea I have right now is it being related to the number of tabs open, since the two profiles seeing the issue have probably over 100 over multiple windows, while the other two only have a single window with maybe 10-20 tabs. Through opening a number of heavy tabs I could not recreate this yet. A restart doesn’t fix it either, meaning the tabs in their unloaded state would still contribute if that were the cause.

mpv

Is this HiPER Calc with ads? Did the free version have those?

Please show me the ways

Media integration should be done via mpris which ff does natively now, so that’s no longer done by the plasma addon