I have tested adding : ${LANG:=en_US.utf8}; export LANG to /etc/profile on a fresh installation.
After apt-get install locales, locales was reporting en_US.utf8 correct.
python -c "import locale; print(locale.getpreferredencoding())" was also answering UTF-8, but the sql lite library still was showing emty folders.
The sqllite library update with pip install --upgrade Mopidy-Local-SQLite is working