It just got reset during the update. To set it back, tap the hamburger buttons (three lines, lower right), tap Settings> then scroll down to Close Private Tabs (When Leaving Private Browsing)> toggle that to the OFF position (gray). In that position, every time you open the browser it will open to a Private tab. In the ON position (green), when exiting the browser it will close any open private tabs, so that when the browser is opened again it will open to the default, basic, not private tab. Hope this helps.

This is a good workaround.

However it has a limitation.

@Mozilla Please add an option to make tab mode selectable.

I like the option of closing tabs on exit.

So I need both.

Settings >

Open new tabs as: [default, private, last used]

Close tabs after exit: [on, off]

Thank you.

Hi,

I also have the same annoying problem, and it manifested itself quite recently.

Just until a short while ago, it worked perfectly well:

New windows were private per default, and all private windows were closed when exiting Firefox.

The workaround that @lpsears63 provided is better than nothing, but by far not as good as the solution that was already there!!