Aaaargggghhhh, these apps will give me some grey hair!
Now I tried to download the Crowdsourcing Reporter App so see what I can do with it but when I click download app and then done (after reading the instructions of course) nothing happens! The same for the Crowdsourcing Manager App Template. Also tried from the map related templates e.g. Find, Edit, and Filter but again nothing happens when I click Done.
I figured it out using Firefox instead of Chrome: In firefox I got the prompt that the website is trying to open another window -> opening the corresponding github page where I can now download the zip-file.
To be honest: On the github page it's very confusing because it says
But actually you are not downloading it from the Portal/ArcGIS Online page but from the github page where I already am. Instead it would be better to put a link there to show where the "Download zip-file" button is, because I didn't see it when I went straight to github (because I thought that's where I would find it...).