Ask HN: How do HN webdevs ensure cross-browser support for websites/webapps?

Hi all, I'm starting a new project and I was just curious as to when HN thinks the best practices are for automated testing of support for multiple browsers.

Selenium looks interesting, but I want to do a bit more research (as I'd rather avoid replay testing within a browser), and am having trouble finding any alternatives.

Something that came to mind is scanning the code base to look for unsupported JS calls (e.g. `Object.entries`), CSS selectors/properties (e.g. :not(X)), HTML tags and attributes, etc. but I haven't seen anything about this.

I'm sure there are lots of creative solutions, what do you use? Why do you use it? What are the pros and cons?

Thanks.