I have not kept up with all the posts in this thread. My personal understanding would be that, unless the Pope says otherwise, that communion on the tongue cannot be forbidden.
However at my parish, the rule (not sure if it’s been the rule all along or if it’s new) is that if an EM or EMHC touches any part of a communicant’s mouth or face, they must step out of line, presumably to go to the washroom and clean up. I do not know if they would get to come back. That is an inconvenience (minor yes, but irritating nonetheless) to those who were in that line.
I know that peoples’ hands can be more filthy as their mouths and I would hope people who receive in the hand are conscious of how the (lack of) cleanliness of their hands could be impacting the health of those who receive after them.
I will just say that receiving communion is, BY DEFINITION, a communal event. Regardless of however you wish to receive, please do so (or refrain from receiving) in a way that benefits the community!