> Definitely, Germany strongly believes that a document that hasn't been a physical piece of paper at least once can't be real.

I'm sorry to tell you that is a an oversimplification and especially for documenting expenses as a company/freelancer it's kind of worse.

Last time I checked if you want to follow the tax law to the word you're not allowed to change the medium:

If an invoice came as a paper copy (e.g. by snail mail), this paper copy is the original. If you scan it the digital version isn't.

If an invoice came as a digital document (e.g. a PDF by email), this digital document is the original - a printed version of that digital document isn't.

So if a tax inspector asks for "originals" it's technically almost impossible to provide them in the sense of the law. If even a tax inspector would care is another question.