Hi,
Last week I posted a similar question
here, but I haven't had time yet to look at the problem.
I haven't tried to remove the built-in fonts yet as tshering suggested, however, I did patch the nickel file using pipcat's code.
I tried to replace the default Georgia with Bookerly, but the result is strange. In some place, font was changed, but not in others. Unfortunately, the 2 most important for me are the book titles and dictionaries are not displayed properly. I will post some screenshots as I get home this evening.