The update from firefox today interferes with the layout of the reading list. It places the [last chapter read/newest chapter] box underneath the chapter title, on the left side. Which, not only, goes directly against an update done a few years ago, but is also very inconvenient. Since I don't expect that mozilla will fix this. I can only hope you can fix this. Unfortunately I can't give you a picture since I don't get the option to browse my device to upload my screenshot.
I don't really use NU on my phone, but I checked on FF for Android, FF Nightly and Chrome and the box it under the series name in all of them. Are you sure it was different before?
I open the reading list dozens of times a day every day on my phone. I would not miss such an inconvenience. The chapter numbers have always been on the right side.
It'll be helpful to provide what version your FF currently is, so they can look for bugs for that version specifically.
79.0.4 (Build #2015757665) AC: 48.0.14, c6965e12d GV: 79.0-20200720193547 AS: 61.0.10 Is what I find when I look for the buildnumber in the app.
My view has shifted when browsing the normal site. Before everything was neat and compact and now its out of place for me. It wasn't like this before I went to work. It seems like it's fixed now.