What is the lowest ceremony way to start building a TypeScript SPA? I would love to avoid Webpack if I can :)
The only thing you need to build a SPA is Javascript, the DOM and history API. You literally do not need anything else. You can use CustomEvent and ES5 properties to observe a model changes, use string templates for the view,use event delegation to facilitate event handling, and implement MVC/MVP/MVVM yourself (3 classes...), you don't need a framework for that.
Obvsiously you'll need a test runner, if you don't do automated testing, you can just download jasmine and run tests in the browser directly without the need to install node.js at all.