Diagram Designer is not available for Linux but there are plenty of alternatives that runs on Linux with similar functionality. The best Linux alternative is diagrams.net, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 50 alternatives to Diagram Designer and many of them are available for Linux so hopefully you can find a suitable replacement. Other interesting Linux alternatives to Diagram Designer are Pencil Project (Free, Open Source), yEd Graph Editor (Free), LibreOffice - Draw (Free, Open Source) and Dia (Free, Open Source).
diagrams.net (previously draw.io) is a free online diagram drawing application for workflow, BPM, org charts, UML, ER, network diagrams. No login or registration are required and features include the ability to save locally (including SVG), a range of stencils, .
Draw lets you produce anything from a quick sketch to a complex plan, and gives you the means to communicate with graphics and diagrams. With a maximum page size of 300cm by 300cm, Draw is a an excellent package for producing technical drawings, general posters, and much else.
PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams. The generator can be run anywhere within JVM and integrated with various application such as wiki, text editor, IDE, programming language, documentation generator, and others.
Vectr is a free graphics editor. Vectr is collaborative like Google Docs, and runs both in your web browser and on your desktop as a native app. With an intuitive interface, Vectr is easy to learn and use.
Draw, part of the Apache OpenOffice suite, is a graphics editor that gives you the tools to communicate with visuals and diagrams. With a maximum page size of 300cm by 300cm, Draw is powerful tool for posters, graphs, charts, and more.