I am trying to improve our appeal for members of the public who come to our monthly lectures (astronomy) who have hearing loss. Thus it will be a fresh speaker each month, most of them Windows users, a few Mac. I'd have to persuade each one of them, in turn, to adopt some form of live or pre-set subtitling.
We already have a good hearing loop system and AV. I don't want to go down the hand signing route with its various languages & dialects and with the inevitable expense for professional signers (probably greater fees than we give our lecturers).
Subtitling for presentations is mainly for audio/video portions. Each presenter would have to already have their presentation saved with embedded subtitles, as the subtitles are embedded into the media files themselves, not the slides. I don't know of any "live" subtitling options.