Obligatory "check your library". It isn't "literally anything ever published any time" like piracy is close to, but in a lot of places (at least in the US), there's a pretty meaningful selection of content you can borrow perfectly legally.
So, on my (Android) ereader, I use einkbro which is a browser that will save pages to epub, then can be used and organized with most reader software. You can also combine multiple web pages as chapters to the same book pretty trivially.
I don't have a suggestion that perfectly fits your question as asked, but figured I'd suggest it anyways because it serves a relatively similar goal for me.
I'm saying they are probably being charged some portion of website sales specifically by the vendor of the web service provider. Which realistically makes sense, because regular online retail already almost always takes a percentage and there are significantly stronger regulatory requirements around anything medical.
I hate this. I'd be perfectly fine with network bullshit if it was a universal standardized profile so it actually worked (and I could build a programmable physical remote for it) . But the App Store is flooded with "android TV remotes" that maybe support one specific obscure (unlabeled) TV. I've never found one that works for anything I've owned.