I wonder what the legal basis for this is? Is there a constitutional provision that allows banning of parties that seek to end democracy?

If so, I wonder how that would work for someone that wanted to end electoral democracy, but not for any malevolent purpose? For example, instead advocated for a different or non-electoral democratic system, but still with noble intentions? For instance, under the German system, could a party lawfully argue to a system based on sortition?

In sortition, public offices are assigned by lottery, as we handle jury selection today. It doesn’t guarantee the most competent leader will be elected, but elections also clearly don’t select for the most competent leader. The main advantage of sortition is that, unlike elections, it doesn’t select for the most power-hungry and psychopathic members of society. It’s long been said that no one who actually wants power should be given it, and sortition is a way of solving that problem.

Could someone in Germany advocate for moving to sortition, or would that violate some constitutional provision meant to protect electoral democracy?