Hello 👋
Flarum is a SPA, so if you're looking for the HTML of Flarum you will need to look at the JavaScript instead. Our docs go into this regarding transpilation here: https://docs.flarum.org/extend/frontend
As for the CSS, this is generated from LESS. You can pretty much override anything using the Admin Area - Appearance - Custom Styles input. Any CSS (or LESS) added there is picked up inside the compilation of your CSS, so editing any files from Flarum is not necessary.
I hope this helps, do ask if you have more questions.
