- Open publish/index.html in your browser.
- Click the "Connect" button.
- Wait for it to finish.
- Flash just like you would've on older firmware, using ReWheel / ffmwheel / you name it.
- Does this actually work?
- Yes.
- Is it permanent?
- No. It "locks" again if you restart your board while still on 5100.
- Is it dangerous?
- No. What you decide to do in FWU afterwards most likely is, though.