I recently downloaded the さくら荘のペットな彼女 light novels as epub files. I've been trying to look for a web browser epub reader so that I can use Yomitan for mining, however, the websites I've found seem to be having trouble loading the format properly. Does anybody have any alternatives? If not, is there something that I could set up that acts as an alternative to Yomitan which can be used on any PC app for mining/autocards instead of only the browser?

This may help https://reader.ttsu.app/

It's better than your regular reader as it renders the furigana well. It also renders the pages in the proper orientation. This is specially built for reading light novel epubs.

and also you can read it horizontal

Sorry OP i don't really know where you can get such sites but may I ask how you got your LN epubs? I have been trying to find some official (and unofficial) ways to get a softcopy for LNs as actual books are way too expensive if I want to get them from Japan itself

https://yatsu.moe/

Lifesaver, thanks so much

I found this a few days ago and it's so so good, I think it's built on top of ttsu reader and it has all the features ttsu is missing. Big recommend.

Use Yatsu instead, it's a newer version which is much better imo

What I had to do back in its time was to but them on Amazon, pass them to my old kindle and then I would be able to rip them.

I highly recommend buying an e-reader like Kindle or Kobo, then you can buy from Japanese stores for very cheap (even cheaper nowadays that the JPY is weak). You won’t be able to easily rip it to use in third party readers but (1) the e-reader is much easier on the eyes anyway and (2) the stores do allow you to read in browser and their mobile apps.

The only issue with an e-reader I think is that selecting text to look up the word in a dictionary is a pain, but 100 pages in and your fingers will subconsciously develop muscle memory. (Reading manga on e-readers is also not a pleasant experience but this post concerns only LNs so…)

I have a Kobo and it beats the dozens of third party desktop epub readers I have tried and it’s not even close.

Buy them from any storefront except Amazon, and then use Calibre to remove DRM, which will allow you to open them in any e-reading program on any device instead of just the proprietary ones.

Sorry for being a lazy ass, but what are it's benefits over Ttsu?

I would highly recommend making the transition to 縦書き sooner rather than later if your goal is to consume native media, especially physical. Even the most stern holdouts I've met who've made the transition tell me it's not as hard or scary as they thought it would be.