Inkscape

see https://inkscape.org/

Inkscape is a professional vector graphics editor for Linux, Windows and macOS. Whether you are an illustrator, designer, web designer or just someone who needs to create some vector imagery, Inkscape is for you!

There are several alternatives vector editors listed at alternativesto.net. Dia is a powerful diagram editor with limited control of graphics. Scribus is far and away the best desktop publishing application, but some alternatives exist.