What is the way to open URLs in firefox private window?

[stefanos82]

I have tried this

but it would not work; it would throw

What is the way to configure this as my custom external web browser?

[guihkx]

Are you using the Flatpak version? If you are, you need to do this.

If you're not, click on "Show Details..." to maybe get more information.

[stefanos82]

It just opens an empty browser window, not even in private...

[martinrotter]

re-test it in latest devbuild release please, other than that hard to say what could be wrong, it works here

maybe on linux the CLI parameters have different names, also do not forget the %1 in parameters

[stefanos82]

Is it possible to test it with version 4.0.4 in a Linux environment, preferably GNU / Debian via virtual desktop?

If not possible, I could just mark this as answer and live with the current given option.

[martinrotter]

4.0.4 version was released when dinosaurs were still present in live form on this planet.

Test it all with latest AppImage jesus and do not use ancient software.

[stefanos82]

I use whatever Debian is offering me.

Anyway, marking as answer.

[guihkx]

I use whatever Debian is offering me.

You could try the Flatpak package. Though, as I mentioned initially, you'll need a specific workaround to bypass the Flatpak sandbox.