Open source alternatives to Lucidchart

D

drawiov32.6.10jgraph/drawio

draw.io is a JavaScript, client-side editor for general diagramming.

E

excalidrawv0.18.1excalidraw/excalidraw

Virtual whiteboard for sketching hand-drawn like diagrams

M

mermaid12.3.0mermaid-js/mermaid

Generation of diagrams like flowcharts or sequence diagrams from text in a similar manner as markdown