From the developer:
It’s called Komga, it’s open-source, and you can find it here: https://github.com/gotson/komga
The target is to be a Plex for Comics/Mangas/BDs, I add new features regularly, but it’s still pretty new (started in August 2019).
At the moment the feature set is roughly equivalent to Ubooquity, but it packs a proper REST API so integration is easier than with OPDS only (it does OPDS too).
There is an official extension for Tachiyomi, which is a very good Android reader (mostly to scrape manga sites initially).
OPDS is supported, and if you have an iPad i would recomment that route, either with KyBook or Chunky.
I compare all the readers i tests on the github page, with compatibility reports.
At the moment some of the features for die-hard comic fans will still be missing: it doesn’t read ComicInfo.xml (it’s on the way), it doesn’t handle story arcs like Mylar do.

Great suggestion!