One of the lesser known alternatives for graph visualization, at least in Europe, is Tom Sawyer Software's Perspectives line of products.
Look at https://www.tomsawyer.com for the company's website and https://www.tomsawyer.com/products/perspectives/index.php for more information on Perspectives.
This is an advanced graphics-based software to build enterprise-class data relationship visualization and analysis applications. It features a complete Software Development Kit (SDK) with a graphics-based design and preview environment that lets you build, test, and deploy graph visualizations more easily, based on a reference architecture.
A visualization of Tom Sawyer graph is given as follows: