Penpot

Penpot provides tools for developing interfaces and prototypes, with official resources explaining collaboration and the options available to teams using its open source software.

It is useful for investigating a particular design or software-development task. Its focus includes Interface design, Prototyping and Open source collaboration, helping a visitor identify the relevant product, technical resource or asset and relate it to the work being undertaken.

The official Penpot site includes sections for Prototyping and Design systems.