According to some sources, Bergamot, a project focused on providing private client-side machine translations in a web browser - and got funding from the EU -, is making a great progress on getting integrated into Firefox. Kelly Davis from Mozilla published two (1, 2) demo videos on YouTube.
I really look forward to this! Google Chrome has translations, but they don't work offline and send everything to the cloud instead. Currently whenever I need to translate something, I use DeepL. For the languages it supports, it provides far better translations than Google.
But an option to translate texts completely client-side, so that no data is leaving the computer, is an even better option, especially for sensitive information.