I finally present the project. You might already know it under the project
https://github.com/BoboTiG/ebook-reader-dict, and this is a rebranding. Still open-source for monolingual dictionaries, and it won't change.
Discover the most comprehensive universal, multilingual and monolingual dictionaries powered by Wiktionary. Bimonthly updates, 180+ languages supported.
The supported devices list is quite large: from Kobo to Kindle to PocketBook/Vivlio to OnyxBoox, to any app like KOReader, GoldenDict, and so on.
Link:
https://www.reader-dict.com
Monolingual dictionaries are, and will always be, free to download.
If you want to go with a bilingual/universal dictionary, here is a coupon to get 10% off: KICKOFF10 (only 50 free slots, first come first serve).
Happy reading!