Home page for the entire suite (in French) with some screenshots: https://lasuite.numerique.gouv.fr/
Code bases are on GitHub and they use English there: https://github.com/suitenumerique/
Dev handbook (in English): https://suitenumerique.gitbook.io/handbook
Not French and I can't say I personally tried deploying any of them, but I've been admiring their efforts from afar for a while now.
Grist https://www.getgrist.com/
A write-up of how the French gov uses it https://interoperable-europe.ec.europa.eu/collection/open-so...
Does grist have forms?
For what it's worth, which isn't much because this is probably outdated: I remember trying grist a few years ago and leaving mildly unimpressed with form support (I think because I was hoping to have image upload in the forms and that wasn't supported yet).
Since it is relevant here: support for uploads was code written by a French contributor, and reviewed by a developer working for the French gov (ANCT/DINUM) and a developer working for Grist Labs. Grist Labs has since maintained and improved on it. The forms feature itself was inspired by an integration built by Camille Legeron at ANCT.