The German Market plugin requires the WooCommerce Tax API, which is only available starting with WC 3.7. In Germany, there are actually just three choices: Either you use German Market, you use Germanized for WooCommerce / WooCommerce Germanized, or you use an actual professional, ie. a lawyer specialized in online law, which is of corpse much more expensive vs. prepared text + a quick checkup.
My guess is, that WooCommerce, as most WordPress plugins, was never really meant / tested for international use. Hence all the issues with eg. Table-based shipping calculations. And thus, also the issues with a non-existing Tax Calculation API / class framework. Just think of: The US with its semi-non required VAT system vs. the REQUIRED VAT in Europe and related countries (eg. the Commonwealth of Nations).
Its not so much about GDPR, its mostly about required = mandatory taxes. Eg. here in Germany, the current mandatory (!) VAT on regular products and services is 19%, and for nurturous food (in theory) and books and several other “essential” things its 7% (eg. the Deutsche Bahn got their VAT reduced by decree during the current CoVid-19 crisis, from “service” 19% down to “essential” 7%).
cu, w0lf.