Is that website down, or maybe it doesn't work in EU?

Edit: NVM, just took a few refreshes to get past the "oh noes" screen

Works in NL

It doesn't really "find" any personal sites, you have to tell it about each manually with a pull request: https://github.com/MarginaliaSearch/submit-site-to-marginali...

This isn't true, Marginalia Search has a crawler. The guy who runs the site writes a lot about the trials and tribulations of running a web crawler on his blog if you're interested. https://www.marginalia.nu/log/ I just checked and my site is listed despite me never manually submitting it. I guess if nobody links to your site, you would have to manually submit it due to it not showing up in crawls, but that's true about any search engine.

That form is just to insert domains that aren't found automatically.