As a result I wrote some go code ( https://github.com/fishy/url2epub ) for the past 2 days, to generate ePub from URL. I also implemented reMarkable API to send them to reMarkable tablets directly.
The current UI for it is implemented as a Telegram bot ( https://t.me/url2rM_bot?start=1 ), running on AppEngine (code: https://github.com/fishy/url2epub/tree/main/appengine ). I initially considered making an Android app for the UI, but decided that Telegram bot is less work for me, and works good enough for this use case (sorry for people who don't use Telegram, but this also means that people on iOS, desktop, etc. will be able to use it).
For the future, I might do:
- Expand the URLs supported (currently it only supports URLs with an AMP version provided, and the AMP version does have article tag inside) - (if there's enough demand for this) Remove the reMarkable restriction, so if you don't have a reMarkable account linked, it sends the ePub file back to you instead. - Provide REST API on AppEngine - Create an Android app