Part of plantuml is graphwiz ( https://graphviz.org). What I didn’t know, you can use itseparately without plantuml.
And there is really a lot you can do ( see : https://graphviz.org/gallery/)
• The DOT Language
• Command-line Usage
• Output Formats
• Node, Edge and Graph Attributes
• Node Shapes
• Arrow Shapes
• Colors
Stay healty
Rainer