I know that one thing I don't like about https://weworkremotely.com is that many of the listed jobs are not truly remote (they are limited to one country). At least on this board I can filter those out.

I think the term "transnational" would fit what you are describing better than the term "truly remote." The US is a very large place. Someone working for an SF startup from their Florida home is just as "truly remote" as someone working from Mexico, Canada, etc.

or http://nomadjobs.io/ , its very interesting that they all are charging $200

One of the key differentiators is the ability to see which jobs are truly remote (like nomadlist does) vs. remote within a particular region. The other is that this job board is focussed solely on coders (whereas weworkremotely also caters for designers, business admin, etc). Hence the optional Github authentication.

or http://wfh.io

or http://remoyo.com