many people in Belgium speak English as there are many expats around Brussels : EU, NATO, ... and companies or lobbyist wanting to be close to EU, NATO etc

The Belgian government on their sites uses four languages : nl (dutch), fr  (French), de (German) - i.e. the official languages and en (english)

see Belgian government site : https://www.belgium.be

please add a locale to be able to use the english language in combination with Belgian locales : number, amount, date, currency etc formats

Locale info can be found here : https://www.localeplanet.com/icu/en-BE/index.html

It can be based on the nl_BE locale just changing the language