Content in only non-default languages

So I have an article-like content type and two languages de (default) and en.

Some articles must be in en only.

content

After a migration from another CMS, there are in fact articles in en only, so only (i.e.) article.en.txt exist for those articles.

blueprints

There is a date field, which should not be translatable, because the date should not differ between languages and also an update of this field should not be accidentally be made in one language and not in the other.

If I set the field translate: false and I only have an en content file, I can see the date but cannot update it in en and it is empty in de.

Cannot sort articles properly when the current language is de, because the date fields are empty, so I need to implement a custom hacky search for the right field value.

When I create an article via the panel, a de content file is created, although I might only want an English version of the article.

Making the date field translate: true results in the first mentioned problem.

So, what this situation really needs is some kind of setup, where default languages do not exist, and where I can create pages in any language, without having a mandatory language version created along with it.

Are there any solutions I do not see?

I don’t think that’s supported in any way.
Even if it’s empty (except for the date), you want to have an article.de.txt.
Then filter for articles that have content. The filter could either work with some heuristics (only articles that have text) or an explicit toggle field in the panel:

$articles = $articles
  ->filterBy('text', '!=' , '')
  ->sortBy(fn($page) => $page->date()->toDate());

//or

$articles = $articles
  ->filterBy('hasContent', '==' , 'true')
  ->sortBy(fn($page) => $page->date()->toDate());

This setting can only be used with the default language.

And the content file for the default language is automatically created when you create pages through the Panel, anyway. There is no way around that.