I decided to use a different Chromium profile for running some extensions, including translation extensions. Problem is I'm running under a Swedish locale, and me changing settings to translate into English in the extensions did not work; they were just ignored.
Finally in the custom desktop file I've made in order to launch a separate profile for Chromium, I put in a language environment variable on the execution line:
Exec=env LANGUAGE=en chromium --user-data-dir=/path/to/my/custom/profile/directory