How to move the language code after a subfolder in a link?

I’d like to establish a blog in a subfolder of a site, so that the link structure would be like testsite.test/notes . But as there would be several languages in use, I’d like to have them working like testsite.test/notes/en instead of the regular order of testsite.test/en/notes .

I guess a crude solution would be just to setup the blog in that subfolder as a site of its own, but I believe there must be a more elegant way. So that both the main site and the blog would be based on the same installation. With routing somehow?

Could get a bit complex with multi language routing, but yes custom routes could be a way: Routes | Kirby CMS