Yoni Arndt wrote in the introductory letter: "My primary research goals
now are to find out: the families: ARNDT, MEYERHARDT, COHN >from Schneidemuhl."

I am not familiar with the status of the ARNDT Jewish family name in
Germany or more specifically with the ARNDT family of Schneidemuhl but I
would be very suspicious that this was not a name change >from AARONS,
ABELES, ARNSTEIN etc. I have seen such name changes in the Habsburg Empire:

AARONS > ARENS AHRENS etc
ABELES > ANNINGER ANINGER AREND ALNER etc
ARNSTEIN > various names

Is ARNDT a bona-fide German family name taken at the time names were adopted?

Celia Male - London, U.K.