>> Unfortunately, Google seems to have the ability to arbitrarily flag any domain and make it immediately unaccessible to users. I'm not sure what, if anything, can be done when this happens, except constantly request another review from the all mighty Google.

Perhaps a complaint to the ETC for abusing the monopoly and lack of due process to harm legitimate business? Or DG COMP (in the EU).

Gather evidence of harm and seek alliances with other open-source projects could build a momentum.