MacOS 12 Monterey was released October 25, 2021. There are no new system languages or spell check languages, but several new language keyboards: Amharic (Ge'ez), Assyrian (Syriac), Fula (Adlam), Igbo, Navajo, and Rohingya.
The keyboard shortcut to bring up the Character Viewer (Emoji & Symbols) has been changed to Fn E.
A list of help articles for Monterey on language issues can be found at this page.
Other new features according to Apple’s notes are:
+New dictionaries for India: Urdu–English, Tamil–English, Telugu–English, and Gujarati–English.
+New thesaurus and idiom dictionary for China mainland
+New dictionaries for Hong Kong: a Traditional Chinese–English dictionary of Cantonese colloquialisms and a Traditional Chinese dictionary of Standard Mandarin with Cantonese pronunciations.
+Suggestions for Cantonese and Shanghainese: Type words and phrases in Cantonese and Shanghainese more easily when using the Simplified Chinese keyboard.
+Magic Keyboard now supports keyboard shortcuts for over 100 layouts, automatically adapting them for the layout you’re using.
+On-device dictation: Available in Arabic (Saudi Arabia), Cantonese (Hong Kong), English (Australia, Canada, India, Singapore, UK, U.S.), French (France), German (Germany), Italian (Italy), Japanese (Japan), Korean (Korea), Mandarin Chinese (China mainland, Taiwan), Russian (Russia), Spanish (Mexico, Spain, U.S.), Turkish (Turkey), and Yue Chinese (China mainland).
+Neural text-to-speech voice in more languages: Swedish (Sweden), Danish (Denmark), Norwegian (Norway), and Finnish (Finland).
+Mixed English and Indic language support in Siri: You can ask Siri to play your favorite song, call a friend, and more using a mix of Indian English and your native language. Nine languages are supported: Hindi, Telugu, Kannada, Marathi, Tamil, Bengali, Gujarati, Malayalam, and Punjabi.
+A new SF Arabic system font features a refined, contemporary design that is integrated with the SF font, providing a clear, cohesive reading experience.