I am using de-DE-ConradNeural and de-DE-KatjaNeural to synthesize german text. They seem to be able to recognize some english words and pronounce them properly in English - but not all.
Using SSML tags <lang xml:lang='en-US'>xxx</lang> it seems to be possible to force Conrad and Katja to pronounce the terms in English. But this "trick" does not seem to work at all when using it with french or italian words - Conrad and Katja will ignore <lang xml:lang='fr-FR'> or <lang xml:lang='it-IT'>and read the foreign words as if they were in german.
Is this behaviour correct and is there any workaround, other than spelling the words in IPA-phonetics, which is very clumsy to handle.