But as far as I understand the main value proposition might be for non-EU citizens to be able to open a business in the EU remotely with access to the EU market, banking system etc
(1) see the section about “inbound Tätigkeit” here https://www.dittmann-hartmann.de/Fachgebiete/Gesellschaftsre...
I knew people doing this without reporting their foreign company income to their local tax authorities, but if they catch you you're looking at severe fines and possibly jail time. I knew a British guy living in Sweden making money from his UK company without fully paying Swedish taxes on his gain from the UK. He later got slapped with a equivalent ~80k Euros fine by the Swedish tax authorities. Turns out, governments don't like you cheating your tax dues.
Legally avoiding taxes in the EU is pretty difficult for the average person without completely relocating to a tax heaven.
So be careful and hire dedicated tax attorneys with experience in international/EU tax laws before you think you're clever and dream of dodging taxes like you're Amazon all on your own.
If you live in Germany but operate a UK company and all those profits never leave the UK, then you'll pay no German tax on those gains. But if you were to take those profits from the UK to use in Germany, then the German gov will want a sizable piece of your foreign gains.
From my limited understanding this is wrong and you should consult a tax advisor before attempting do set this up. “Ort der Geschäftsleitung” (smth. like “location where business decisions are made”) seems do be a recurring topic when it comes to taxation of foreign companies in Germany. They might argue you are “unbeschränkt steuerpflichtig” in Germany. (You owe taxes just like if your company was registered there.)
Paying taxes in the Netherlands, doesn't absolve you from also being taxed in your home country, if that's where your profits from the Netherlands will end up eventually.
So, for me the uncertainity and tax complications were at the end not worth the upsides of less bureacracy to register an Estonian legal entity.
If the customer(s) of your business are in Spain, then you would almost certainly find it least complicated to setup a business in Spain. As a legal resident of Spain, you are already required to pay taxes there.
From what I've seen, the tax rates quickly surpass those of the US; so you'll pay all your taxes to Spain and owe the US nothing (although of course you still have to file).
However... if your customers or clients are US based, then you could setup an LLC in a favorable state like Wyoming (you can search on this topic of course; and my serious search resulted in Wyoming seeming to be best). Then your US clients will not face any perceived or real obstacles in doing business with you; and your tax work should be easier (getting qualified help).
It's like blaming her for a compromise on her website. Do you think she has any idea that her wordpress (example) was an old version?