I currently use it across multiple devices: KOreader supports it on Kindle,Kobo,Linux,Android Foliate (great EPUB reader) supports it on Linux On Android - M

I currently use it across multiple devices: KOreader supports it on Kindle,Kobo,Linux,Android Foliate (great EPUB reader) supports it on Linux On Android - MoonReader and a few other apps. Ubooquity app for eg. On iOS- I use KyBook, and I’ve been planning to work on something that integrates this into the Files app. The mobileread wiki has some more, but the page has some spam: https://wiki.mobileread.com/wiki/OPDS https://wiki.mobileread.com/wiki/OPDS