When I used the MySQL English docker installation method I could obviously pick the dutch language in the xwiki interface, however this did not change the ‘main pages’ such as frontpage/sandbox/helpfile/templates.
Now I understand that these can be translated manually, however I’m hoping that there’s a more straightforward way to install xwiki in Dutch (where all the templates/frontpage and such) are immediatly
The UI translations are not stored in the DB (the few wiki pages one are though). They are stored in the XWiki WAR file and thus you always get all the translations. The way you install XWiki doesn’t impact translations. You just need to configure your wiki to use dutch. See https://www.xwiki.org/xwiki/bin/view/Documentation/UserGuide/Features/I18N
Every translation you contribute on https://l10n.xwiki.org is automatically committed (trough some validation but more to track technical issues that for the quality of the translation) and should end up in the next release.