I figured you had a good reason to remove compatibility, it's fine, I managed to make it work anyway

The renamed version has separate settings btw, it doesn't seem to have caused any problems with the original.
I used flaresolverr sometimes in the past but it's quite slow for me and often didn't work, so it's not my favorite. I prefer to be able to do it in the background without having to manually open every fic so while the other options are great to have, I'm too lazy to use them often.

I totally forgot about nsapa's proxy since I couldn't figure out how to install it back when this all started, but I did it now and it works well! Thanks for the reminder!
I couldn't resist doing a little test. To download the same (18 chapter) fic
Nsapa took 3:58,
Flaresolvver took 4:42,
Fanfictiondownloader took 3:08, minus the negligible time it takes to add it to calibre.
My slow_down_sleep_time setting is 10, and in Fanfictiondownloader I set the delay to 10 as well for this test. I normally have both the delay and dynamic delay at 6, and it took somewhere between Nsapa and Flaresolvver with those settings.