I almost exclusively use private tabs and had quite a few of them open at any time for things I was working on. But apparently since I’ve last updated the default behavior changed to close private tabs and the option to keep them open was removed.
Digging into it, I’ve found the bug report in the link. The last entry in the bug report is concerning:
It looks like this was discussed in FXIOS-8672, although I don't have access to that JIRA to take a look at the discussion.
Of the three PRs that I see that reference FXIOS-8672, one of them mentions:
I've intentionally kept this PR as simple as possible so we can release it and then be sure there is no major blow back from users. If we need to roll back it should be very simple in the current state.
I'm not sure what would count as "major blow back" but there is at least some hope that this functionality can be restored.
I agree with @garnetred that this behaviour isn't limited to force closing the app.
You might consider seeing if Container Tabs paired with the Temporary Containers addon serves your need. With that setup, every new tax you open is isolated from the local storage of your other sessions, much like private browsing. You can also set up defined containers for sites you want to remember the state of.
Oh, if I could add add-ons to iOS, this bug wouldn’t exist:
As of now, the only way to have a page not leave cookies and local storage in your device when you leave it is by opening it on a private tab.
Oh crazy, there's no add-ons on iOS? I had no idea; I avoid Apple.
So do I. My company does not. Neither does Mozilla, though it appears they’re changing their mind.