[Resolved][Fresh] How to load data asynchronously after rendering a page ?

Hi ! I was wondering if someone could help me understand the paradigm to load data asynchronously after a page is rendered. My use case is that I load data from the backend, reading some folders and retrieving git information. It takes a few seconds so I don't want to wait for the whole information before rendering the rest of the page. My code runs well if I do that synchronously but I don't understand how to do it after the page render. Should I use a component ? An island ?
I don't understand well which code is executed on the server and when so it's not easy to troubleshoot, and I couldn't really find any examples that do something similar.
I did a post here with more details but maybe it wasn't the right place for it : https://discord.com/channels/684898665143206084/991511118524715139/1072518216728977489
Any help would be appreciated, cheers !