Thanks for the update! We're working to have expected functionality when third party cookies being disabled. I'll keep an eye on when it's planned to be released.
Is there a config flag to enable this?
The option has been in firefox as far back as I can remember. It's in the Preferences, under Privacy; you'll need to select "Use custom settings for history". I've never noticed any breakage, and I assume in-part because iOS and Safari set it as their default a few years back.