I have this in Firefox Android (available for Chrome-based browsers too):
- Read Aloud: A Text to Speech Voice Reader – Get this Extension for 🦊 Firefox (en-US)
- SherpaTTS | F-Droid - Free and Open Source Android App Repository (forum thread)
in Sherpa-TTS I have the languages downloaded I can understand (each 60MB) and set as system service (replacing PicoTTS set in Settings).
Then from the browser Read-Aloud is set to Auto and it picks up the right language depending on article. FF has a reader-mode too for Text isolation. The RL shortcut is behind Settings → Extensions → Read-Aloud.
The Piper voices are pretty good, big step for offline voice - all device local, works in other Apps (OrganicMaps etc) - recommended.