I'm on Firefox Nightly Preview and I've enabled the new "Open links in app" default option.
It works, but when the app is opened, it appears inside the Firefox app when in "multitasking", instead of a separate one. This can cause issues when you want to go back to the browser.
See the attachment to understand what I mean:

Firefox should open the separate Reddit app that should appear on its side, like Chrome does
Also as a side issue: when you go back to browser with back button, you see current website instead of the previous website.
For example:
1- search youtube on google
2- open YouTube
3- go back to browser with back button
4- you see youtube.com is open instead of google
Can someone confirm this?
Yes, I forgot to mention this. Basically you will see 2 times the same website: once in the app and another one in the browser page
@rocketsroger Could FLAG_ACTIVITY_NEW_TASK be used here?
Note that if you disable the global "open in app" option and instead manually tap the same function each time you're on reddit/youtube, everything works as expected
@NotWoods I think you're right, FLAG_ACTIVITY_NEW_TASK will probably fix this, I'll look into this.
@Sangeppato I've debugged the side issue where the page is also loaded on the browser side. In most cases it looks like an redirect was happening when you tap on the reddit link. I can see this with Google searching Facebook post results as well. But can't reproduce with Twitter search results. I'll create an issue for the side effect for further investigation.
Issue opened for side affect https://github.com/mozilla-mobile/android-components/issues/5471
A-C issue for this https://github.com/mozilla-mobile/android-components/issues/5473
main issue fixed by https://github.com/mozilla-mobile/android-components/issues/5473
@rocketsroger
Thank you!