The Nextcloud Forms app is a self-hosted surveys and questionaires app.

* Simple design: No mass of options, only the essentials. Works well on mobile
  of course.
* View & export results: Results are visualized and can also be exported as CSV
  in the same format used by Google Forms.
* Data under your control: The survey info and responses are kept private on
  your instance.

WWW: https://apps.nextcloud.com/apps/forms