Formbricks

Formbricks is an open-source alternative to commercial survey platforms, letting you run feedback campaigns on websites and inside applications. Since the code is public, you can self-host it, keep your data on your own servers, or use their managed cloud. The platform handles surveys triggered by user actions, in-product forms, and traditional questionnaires.

It's ideal for teams that want control over their survey data and don't want to trust a third party with user responses. You get the flexibility of open-source without sacrificing the UX of a polished product. Installation requires some technical setup, but once running, the form builder is accessible to non-technical users.