Open-sourced Google Sheets™ add-on to use DeepL translation without leaving Google Sheets™. Translate the contents of the selected range and paste them in the range of cells adjacent to the original range. You need to have your own DeepL API Free or Pro account.

Please visit the website for more details!
https://www.scriptable-assets.page/add-ons/sheetsl/

Source Code:
https://github.com/ttsukagoshi/sheetsL