I thought specifying 'duniter'’s $HOME to
/home/yunohost.app/duniter to be enough
The config actually went into:
/home/yunohost.app/duniter/.config/duniter_default/
Specify '--home $datadir', so the configuration goes into
/home/yunohost.app/duniter/duniter_default/
Update documentation accordingly with \$HOME to make
the already a long and relative complex command shorter