draw.io - Online diagramming application

Figma - Team-based interface design, Figma lets you collaborate on designs in real time.

Dia - Dia is a GTK+ based diagram creation program for GNU/Linux, MacOS X, Unix, and Windows, and is released under the GPL license.

GEES - GEES is an all-in-one AI design platform that is shaping a future where you can brainstorm, design, hand-off in one file — without changing any other tools.

yEd - yEd is a free desktop application to quickly create, import, edit, and automatically arrange diagrams. It runs on Windows, Mac OS X, and Unix/Linux.

Sketch - Professional digital design for Mac.