I am sorry that you have trouble installing Wikifab. First, know that this package is done to create a wikifab-like website, we didn't update it this package since some time. And we had customized it a bit to create the current Dokit Demo, which has some additional features.
We are currently working on a new version of this package, which may look more like the Dokit demo.
Having said that, I just take the time to try install it using this package : https://github.com/Wikifab/wikifab-main/releases/tag/1.2.0-beta
Indeed I got an error on step 3, that I had to fix by replacing the file "maintenance/initWikifabClass.php" by its latest version, available here : https://raw.githubusercontent.com/Wikifab/wikifab-main/master/maintenance/initWikifabClass.php
But I don't know if this is the error you get, could you describe how it fails ? We are happy to get some feedbacks to improve our process and documentation.
If you still have difficulties to install it, I suggest you to wait that we publish the next version of the package, which should be coming soon (I am working on it this week).
Thank you for your feedback