My favorite flavor, plantuml, available with a cheesy (but very convenient) cli wrapper via npm- https://www.npmjs.com/package/node-plantuml
The --unicode mode is particularly delightful
There's a VSCode plugin for plantuml, it's fantastic.
+1 for plantuml. You can make very useful sequence diagrams with it, in ascii no less.
It would be remiss at this point not to recommend websequencediagrams[0].. been using it for years (and convinced multiple workplaces to shell out for the self hosted version..). It's great :)