Cross-platform readers that remember your current page?

Hi,

I am looking for ereader apps that sync your current page very well across multiple devices. I know of a few applications, but so far, every last one of them has one or more glaring problems:

* Adobe Reader DC: No swipe page turning. Overly complex UI. Unwieldy cloud sync.
* Adobe Reader Touch: Rotten zoom. Poor cloud sync support. Broken support links.
* Aldiko: No desktop support. Their website is a crummy WordPress blog that hosts a single raster image.
* Alreader: Android only.
* BlueStacks: Battery drain.
* BookFusion: No desktop support.
* Cool Reader: No PDF support.
* iBooks: Limited to Apple devices.
* FBReader: No Windows Metro app.
* FoxIt: Can't delete the dummy PDF.
* FullReader: Android only.
* Google Play Books: No Windows Metro app.
* Freda: The bulk item UI doesn't actually perform operations in bulk.
* Kindle: No sideloading on desktop.
* Kitaboo: The login form is invisible.
* Kobo: No sideloading on desktop.
* KyBook: iOS only.
* Lucidor: No mobile support.
* Moon+ Reader: No iOS support, no desktop support.
* Nook: Crashes Windows, no desktop cloud sync, bad launch view, page turn stutter, horizontal swipe direction reversed.
* OverDrive: No sideload/PDF support.
* Prestigio: Android only.
* ReadEra: Android only.
* Scribd: No Windows Metro app.

What is your favorite, hyper cross-platform ereader that works with mobile and desktop environments?

Android, iOS, Windows, macOS, sideloading, current page sync, PDF, and ePUB/MOBI support are a must. Preferably Ubuntu GUI support as well.