Ulefone is offering for the eager fans the Android 6.0 Marshmallow beta update for their Paris model available for download at the fans blog website.
They are also stating that while the final build is still not fully complete yet we can expect it being released in a very near future. But those impatient fans can already download the beta from here so no harm done.
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Keep in mind this is really not the polished final build so you are taking full responsibility for the possible problems and issues. Personally i would maybe wait a little while more for the final build distributed via OTA, but to each his own of course.