The basic flute embouchure should be essentially the same for any sideblown flute. That said, modern flutes manufactured today generally have greatly improved cuts on the embouchure hole. The modern cuts to which we are accustomed may require some embouchure adjustments to get the best possible sound on an older cut such as on a baroque flute. Experiment with minor embouchure adjustments to try and improve the sound. i.e. blow higher, blow lower, change the focus of the airstream to be more or less focused. You probably won't get instant results, but with a bit of time you should be able to improve.
The other possibility is that there may be a flaw in or damage to the embouchure hole. It might be a good idea to to ask an experienced flute tech (preferably one familiar with baroque flutes) to inspect the hole and the blow edge.
"Never give a flute player a screwdriver."