You installed language packs, you need dictionaries (which will show up in a Dictionaries tabs, not Languages in about:addons). Dictionaries column here https://addons.mozilla.org/firefox/language-tools/
Bug 1881830 Comment 4 Edit History
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Based on the screenshot, you installed language packs, while you need dictionaries (which will show up in the `Dictionaries` tabs, not `Languages` in about:addons). You can install one from the *Dictionaries* column here https://addons.mozilla.org/firefox/language-tools/