Bonjour Raphael
By clicking on the CC icon on the lower tool bar, I do get subtitles, but they are also in French, so while they do help a little as so many of our words have common basis, it goes by faster than I can make much use of it!
So sorry to hear of your problems with what is so obviously a beautiful and very capable boiler!!!
After you get the subtitles, click “settings” or the little gear/wheel and you can change them to any language