I’m a big fan of DeepL for translations. Before trying to write more blog posts directly in English to improve my skills, I wrote many blog posts in German and then translated them. The texts were probably better than my non-native English.
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.