OnlyOffice. Has outstanding compatibility with documents
It might be decent, but is isn’t “outstanding”, advanced formatting and features sometimes fails. Another thing about OnlyOffice is that it is a web app, it might work fine for smaller documents, however when you’ve to load a 50+ page document scrolling around becomes really bad as you’ll have to scroll and wait 1-2 seconds for each page to load.
Things like opening PDFs, viewing various video formats etc, are built-in and work flawlessly on pretty much all Linux distros
It isn’t “flawlessly”. Forms in PDFs aren’t supported properly.