How do I build a trilingual NL + FR + DE storefront in Magento?

Belgium has three official languages: Dutch (Vlaams, ~60% of the population, Flanders: Antwerpen / Gent / Brugge / Leuven), French (Wallon, ~40%, Wallonia + Brussels: Charleroi / Liège / Namur / Mons), and German (~1%, the East Cantons: Eupen / St. Vith / Malmedy). A serious Belgian e-commerce store needs all three.

Magento 2 architecture for this:

1. One Magento install, one website, three store views, be_nl, be_fr, be_de. Shared catalogue, currency (EUR), and customer base, but separate translations, URL prefixes (or country-coded paths like /nl/, /fr/, /de/), and per-store CMS pages.
2. URL routing, prefix-based is the cleanest. Add IP-geo + browser-language fallback (Belgian visitors hitting the root see Dutch by default if they’re in Flanders, French in Wallonia, with manual switcher).
3. hreflang, emit per-page nl-BE / fr-BE / de-BE tags. We use Panth_Hreflang module to manage this from DB.
4. Per-store catalogues, product names + descriptions + meta translated per store view. Attribute scope = store view for any localised text.
5. Per-store payment + shipping, same Bancontact / Payconiq stack on all three, but copy in the right language.

For Hyvä we ship a custom language-switcher that lives in the header without a full page reload.