I want a browser with a simple set of command line options that would let me navigate to a page, save the page or some part of it, trigger any of the actions that I normally do with the menu or mouse. Then I would be able to script it without having to install huge unstable things like Playwright and similar.

You can open Chrome with a remote debugging port enabled and send commands to it using the Devtools Protocol. https://chromedevtools.github.io/devtools-protocol/

Does this work headless?