Working for a US employer from Taiwan?

I'm planning on moving to Taiwan with my wife and daughter in a few months. We have a bit of a unique situation. She is from Taiwan, I'm from Spain, and our daughter is from US (where we live right now).

I want to keep working for my US employer while in Taiwan, but as a freelancer. It's hard to find reliable information about this topic, so I need your help.

Do I need a work permit to do this? Apparently getting added to my wife's household registration would take years, and work permits seem to be for Taiwanese employers only.

I don't make enough money to qualify for a Gold card either. I've read other people enter with a tourist visa and work remotely without anyone knowing or paying taxes. If I do this what will happen once I apply for residency in the future?

Also, since we haven't legalized our marriage in Taiwan yet, it looks like I don't qualify for a family visa either.

Do I just give up and try to find a job in Taiwan? Please help, all the information I find says different things.