Hi Stefan,
Survey123 for ArcGIS works with ArcGIS organizational accounts. As Jayanta points out above, you can start with a free 60-day trial, which is exactly the same as the real thing, but just limited in time. It is only the Free ArcGIS Online Public Accounts that Survey123 will block.
I would recommend that you follow the step by step instructions in this help topic: Create an ArcGIS organization—Survey123 for ArcGIS | ArcGIS With these steps you will be able to setup your own ArcGIS organization. As an administrator of the org, you will also be able to invite others to capture data with Survey123, and if you give them permissions even create their own survey projects.
Then, you can right away login into https://survey123.arcgis.com and start building simple surveys from your web browser, or if you want to get sophisticated, with Survey123 Connect for ArcGIS.
I would also recommend a couple of things to get started:
- Join (follow) the Survey123 for ArcGIS GeoNet Group, so you can ask questions to the Survey123 community of users. You will also find in that group a blog with lots of information.
- Watch the Survey123 video-tutorials in this YouTube Playlist
Thanks,
Ismael