ebook-reader VS calibre

https://reader.ttsu.app/ + yomichan

ttu reader (github) is good for this.

An ebook reader specifically for Japanese that supports yomichan: https://github.com/ttu-ttu/ebook-reader

I eventually did most of my epub book reading with tsutsu reader and Yomichan, which was especially nice because you could import a variety of dictionaries, and instantly make Anki cards. At this point I was mainly using J-J monolingual dictionaries, and I needed multiple dictionaries as some words or idioms only appeared in certain dictionaries.

I read books using ttsu reader and a browser addon called Yomichan, it lets me lookup words by clicking on them. I use DeepL if I didn't understand a whole paragraph or section.

Reader for browsers (works with kiwibrowser for android e-readers) https://reader.ttsu.app/

Set up yomichan on kiwi browser and read literary anything on that. You have the entire internet there, you can even use https://reader.ttsu.app/ for epubs

Once you have the epub, you might be able to open it up into a web epub e-reader like https://reader.ttsu.app and use Chrome to MTL. (I haven't tried this myself)

If it's an epub file, you can open it with ッツ Ebook Reader, an online reader (github). The characters count is displayed at the bottom right.

Not to be confused with Calibre, the excellent ebook software by Kovid Goyal:

https://calibre-ebook.com/

Glad you were able to fix it, but what about trying Calibre? It is free and makes it easy to adjust things, add info, and change front covers.

Or using Calibre (pdf or azw3) https://calibre-ebook.com

There are already some very good ebooks solutions out there so there's really no need. Calibre for the backend and database management, Calibre-Web for the front end, and Openbooks for content.