I am thinking about it.
US 501c3 is unlikely (unless my physical presence is not required and someone else tackles this), since I don't dare to ever fly to the US.
At the moment I am more contemplating with UG (German Limited). Would let me sleep better at night. Too many lawyers making a living out of deliberately misunderstanding things and sewing people nowadays (I am talking about the huge increase in cease and desist orders as well as court proceedings).
e.V. is tax-deductible but doesn't provide such great limitation of liability. e.V. It needs at least 7 members. Needless to say, those can't be anonymous.
I just found out, there is such thing as gGmbH which is a tax-deductible Limited. And even better, there is an gUG (Gemeinnützige UG), which is the same, just you don't need lots of authorized capital, 1 EUR is enough. (And only liable up to 1 EUR. No one will give such a company a loan, but I don't like loans anyway.) (Apart from preliminary expenses for the authorities to hand out and look at lots of paper.)
I am not sure time is quite ready for this yet. I hate the time that is wasted on paperwork and not on meaningful things. However, when really required, I'd do it.