In Windows with Qtranslate you can select text from any program(ebook reader, pdf, doc etc.), press some shortkey and translate it. Are there any alternatives for Ubuntu/Linux? There a lot of extensions(like S3.Translator for Firefox) but they just translate something that's in the browser's tab.
I was also using Qtranslate when i was on Windows and missed it after switching to Linux. So i made a simple application for my own need. Hope it can help you too: https://github.com/yasirtug/ni-translate
I got this solved by using Vivaldi Browser, it's a very handy one with many customizable features (including translating selection).
I set a shortcut to translation from the settings, and now it's almost the same experience of that with QTranslate.
Same Qtranslate you can try crow-traslation support for linux, https://github.com/crow-translate/crow-translate