Man pages matching name xmcvtbytestreamtoxmstring in section 3:

XmCvtByteStreamToXmString.3.en	debian 10 / libmotif-dev
XmCvtByteStreamToXmString.3.en	debian 11 / libmotif-dev
XmCvtByteStreamToXmString.3.en	debian 12 / libmotif-dev