I found a quite nice tutorial online that explains all the steps you have to take to do the job.
I couldn’t copy the mmssms.db database like he was doing it.
I had to change to a root shell on my android and copy it to somewhere else on the filesystem and give it other permissions to get it to my machine.
The only thing I „improved“ is the shell one liner (see below) export from the sqlite mmssms.db that marks the newlines in sms the correct way so the tool Harmattan-SMS-Boat can make its job just fine.

#!/bin/sh
sqlite3 "$1" \
"select address,type,datetime(date/1000, 'unixepoch','localtime'),datetime(date/1000, 'unixepoch','localtime'),body from sms;" | \
sed -e 's;^\([^|]\+\)|1|\(.*\);\1|IN|\2;' -e 's;^\([^|]\+\)|2|\(.*\);\1|OUT|\2;' -e '/^[A-Za-z0-9+]*|[IN|OUT]/! s;^; ;' | \
sed 's/|/;/g'