For research, I have always been using Zotero. So no issue. Problem is, Zotero local app does not work only office. First was WPS, but I try being open source, I eventually I had to install Libreoffice. Apparently, Libreoffice looks neat on ChromeOS so I don't complain.
Discussion
For email client, I used Geary. it is not perfect. but it is fine. On Android I used Edison Email, in lieu of the Gmail app.