I vow for open standards and used to upload epub files to Google Play Books and read in my devices (Kindle Fire 8 - with Google Play sideloaded, iPhone, iPad) with decent Sync. In december I got a Kobo Aura 2, my eyes are more comfortable have less distractions but I lost ubiquity and sync, also E-reader feels slugish and dictionary font is very small even with glasses. It's a take the blue/red pill situation.
I'm so sad that WikiReader project, debuted in 2009, was abandoned in 2014.[0]
Hopefully, The Open Book looks more promising & would be able to fully replace WikiReader.
JFTR, Need write an article about The Open Book Project[1] on Wikipedia.[2]
[0] https://en.wikipedia.org/wiki/WikiReader