kpz

If you already have funding these costs are peanuts, but if you just start out or want to bootstrap the running costs of a UG (~1200 yearly?) could be a dealbreaker.

Ah yes, then i would conclude that this is not a simple solution.

Please correct me, but would a start-up don't need to be a Gewerbe / UG / Gbr / ... to have an entry in the Handelsregister? You can't just make up a "company" a filed it as "Einkommen aus Selbstständiger Arbeit" when doing your taxes, can you?

Yes, but are there many risks for a digital startup? (Serious question, i can't really think of any)

Is it a possible for a solo founder in Germany to register an Estonian Business? I had the impression (althought i'm not sure about it and would happily be corrected) you would need to apply for e-residency and need a local contact person for bookkeeping + banking. With the yearly costs being higher than just going for a Gewerbe / UG + local (german) tax advisor.

Would having a "foreign" company have any disadvantages comparing to a german company?

Does anyone know if having a Gewerbe would be just as difficult to transition to a C-Corp?

The whole process of registering a UG or GmbH is ... not so straightforward while registering a Gewerbe (especially if using the Kleingewerberegelung) sounds like a good starting point. Not sure if you can raise money that way though.