Concerning LLC be careful that there are double taxation treaties and that you first find an accountant who specialises in running a LLC from Ger/Aut. Otherwise you’ll pay twice in tax + high fees for the extra paperwork the accountant needs to do locally.
I personally had a look at having a UK Ltd run from Austria, there are plenty of companies specialising in that (just google UK Ltd Österreich/Deutschland). Not sure to what extent that’s still possible post Brexit.
All in all, especially if the big company is willing to pay upfront, I would personally go for a GmbH, might be more expensive to set up but saves you troubles in the long term I think.
Having said that, I’m only a programmer myself, please don’t rely on my advice here, definitely talk to a local accountant about that, they usually have a free consultation to get started.
