Really sorry about that! I think soon with an Electron update, all languages will be automatically supported (similar to how things work in a browser).
@Licat has been working on this since August: https://github.com/electron/electron/pull/25060
In the meantime, any new languages implemented will be replaced once the upgrade happens, which is why we’re currently holding back doing work here.
I understand it’s very annoying, really sorry about that! (I live in Canada too so I think I can feel the pain)
Other than spelling, the current bundled dictionary is also pretty limited. I see perfectly fine words shown as typos all the time. This will be fixed with the upgrade as well.