This add-on uses the online dictionary https://tech.yandex.com/dictionary/
Unfortunately, I didn't find another online dictionary service with more or less adequate quotas for use by free users.
In addition, dictionary articles here are quite detailed.
But, of course, if I can find the best service - I will remake the add-on for it.
It will be enough to rewrite only two modules of the add-on (dictionary.py and languages.py).