Available since LO 7.5 and Mert's e20d2de7836da52dbf9e528d1043b1e188097bfd as an experimental feature. 1. Turn on Experimental Features in Tools/Preferences > LibreOffice > Advanced 2. Set up API key and URL in Tools/Preferences > Languages and Locales > DeepL Server 3. Use the feature from Tools > Translate