I'm using Publisher v 1.7.3 on Mac OS 10.15.2. I have a couple of Tibetan dictionaries installed in the Mac. When I use Unicode Tibetan, I do see the Tibetan option in the typology options. Ligatures and contextual alternates are working fine. I do not see my Tibetan dictionaries as options in the choice of dictionaries, but I don't care about that.
The problem is that Publisher is treating the tsek ( or tseg: U+0F0B ) word separator as a letter. So a whole sentence becomes a single word a