I struggled to root my FP2 after installing FP Open OS until @Irina_Spitznagel told me what to do:
Go to "Settings"
Go to "About Phone"
Tap 7 times on the word "Build number"
Now go back to "Settings"
And you will see a new menu entry "Developer Settings"
Tick the box to root your phone
Edit: added the last three lines thanks to @paulakreuzer and @Stefan
That kind of interface (magic gate/Easter egg) is pretty stupid and will confuse people. I hope this is a joke ā¦ 
Youāll still have to enable root access in the developer options menu.
Well, I think itās good that it is an option that can be enabled easily but is not enabled by default, because some people want to use banking apps and stuff like that that wonāt work on rooted phones. And why is āhiddenā in the Developer Options? Donāt know, maybe it was just the easiest place to integrate it in the Android settingsā¦
Sorry for my honest reaction. But I think this way of rooting the phone makes no sense to me. If I want to root my phone, I donāt want to search for the magic moves online. I want to go to the Developer Options and activate it. Iām not against āhackerā jokes, but in this area it will confuse people even more. But thatās just my opinion.
Can the user āunrootā the phone by clicking the button 7 times again? Just wondering.
No problem with your reaction. Please feel free to share your option.
I edit the subject so that it is more obvious that itās about the FP2.
To unroot you simply untick the box in Developer Options .
Tap often on āAndroid-versionā (Settings/About Phone), later long on the appearing lollipop.
The tapping thing is for enabling Developer Options, and itās done only one time. Then Developer Options are always visible (unless you untick them on purpose inside that menu).
Root is a powerful and dangerous option. I think itās the right place.
Is it possible to disable them again? I tried it once by tapping on the build number - but no way.
I agree, itās the perfect place for the root option.
Also, if you consider yourself a bit of a power user (the kind that need root), the developers option is pretty much one of the first thing your learn to use, if only of the āusb debugā
I agree with everything that you and others have written here. And this is a minor thing, I donāt want to make this bigger than necessary. But what I wanted to point out:
a) Hiding the Developer Options like this is a bit childish. If you want normal people to report bugs quickly and efficiently, allow them to do so. Do not make this more complicated than necessary.
b) Being able to shoot yourself in the foot is an old Unix paradigm, so is root. And many ways have been established to make this less toxic. The system should give the user a brief message that he is doing something that could change the way his phone will work/the Fairphone support will react.
I personally think that reporting bugs easily with all related info is even more important than being able to root the phone easily.
You can disable developer options by opening them, and switching them off in the first line (still in the grey area, not white).
Haha, itās so easy, that I didnāt see it. Thanks!
I sometimes help people with their phones, but it makes me nervous returning the phones with enabled developer optionsā¦
I also think itās in the right place. Most people know about the dev options, as I think they can be enabled the same way on any version of android. So you are even likely to find the root option even if you havenāt specifically looked for it.
On the other hand you have to consider that some users may give their phones to children to play around with and in this regard I think it makes sense to have the potentially dangerous options hidden at least a little bit 
and of course being able to switch it on and off makes a lot of sense for those who want to test it but later decide against it.
Very good design from my point of viewā¦
Actually it is an Android feature since at least Froyo (2.2), it is not a joke or an easter eggs, it is a simple way to prevent ānormalā users from accessing ādangerousā options, but allowing developers to easily access it without modifying the rom.
And I agree, it is the right place for root option.
To hide it again, you may try to clear data for Parameter apps in settings.
+1 on @NicoM NicoM. before seeing his post I was about to say that that way to access the Developer Options has been since as far as I can remember in Android, it is and Android feature. Fairphone is not to be blamed this time (!) so give them a bit of slack.
Iām not blaming anyone, not even Fairphone And I agree with @NicoM.
I just wanted to point out that I always disliked this āfeatureā. The only smartphone I own so far is an FP1. I played around with other phones to help friends and I always disliked it. There is no easy way to find problems fast without usb especially if the phone crashes hard or the display goes off. Explaining this to people how to get there always takes a long time (including how to download adb and use ā¦). Itās confusing. The way to activate the menu is a nice joke, but confusing.
Making this an āeliteā/underground feature to scare people off sounds wrong to me. But as I also tried to point out that this is not a big thing for me, just annoying.
Backup and debugging (using on-board tools) does not work very well on Android for normal users.
This ādiscussionā is going nowhere. For those who got here searching for a way to root your FP2 running FP Open OS please check the first post.