I’m not sure what to make of this, as you say updating TWRP worked, but the at the same time the version number doesn’t change (suggesting it didn’t work), yet you mention successfully flashing openGapps, which doesn’t work with 3.1.1 (suggesting the TWRP update did in fact work as you must be on a different version to not run into zip verification problems).
I can recommend this topic for more background on what people have done to get things working:
I updated TWRP via fastboot. Then rebooted into TWRP, it was the new version. There I successfully flashed OpenGAPPS latest version. But not all Google Apps work and when I rebooted into TWRP again, it was the old version. In the old version, flashing OpenGAPPS did not work (as expected). I did the same thing twice, same result.
I will read the linked topic and give it some time, thanks for your help!
One suggestion, you might want to use TWRP to make a backup of only your system partition before installing OpenGapps in case you want to uninstall them. In my case I just install OpenGapps to get the play store and download my paid-for apps, then restore my system partition.
Android 7 will finally be the point where I switch from a rooted FPOS to FPOOS with OpenGApps.
So, I wonder if this guide is still up to date (and this one)? The questions in this tread seem to suggest some versions and other things have changed. Which links/instructions should I follow and which ones have changed?
The second link in your post is to install the gapps, which is not mandatory (I use Fairphone open OS without gapps form ore than one year now), I don’t know if this part is still valid or not.
The general gist of the TWRP llooks okay, but there are some changes for FPOOS/Android7:
FPOOS comes with TWRP, but this version doesn’t work for installing openGapps. There is a topic about that here. Most success seems to have been had with installing a newer image from here (.img via downloads section). Pitfalls are that in TWRP the file manager browser needs to be toggled from .zip to .img, and that after installing you need to reboot directly into TWRP to avoid changes being reverted.
The openGapps package is still ARM, but now for Android 7.1 (obviously).
I tried to switch to FPOOS with this guide but when I type “sh flash-for-unix.sh” I get this:
sh: 0: Can’t open flash-for-unix.sh
an nothing further happens. Does sombody know what the issue is. By the way i run Ubuntu on my PC
(1) When I press “reboot”, the FP reboots, when I press “shutdown” it reboots also.
(2) WLAN sometimes can not be find. After reboot there is no problem.