I don’t know the first thing about mobile games on itch, but there seems to be a “mobile friendly” checkbox for HTML5 games which currently can’t be filtered for. If that checkbox wasn’t a checkbox but rather a tag, it could be filtered for.
While this isn’t a classical merge suggestion, this thread did not only seem like the closest match but it also seemed like something that could be done in a very similar fashion to the automated merger/replacement of tags in the database.
If I was wrong about that, I do not mind this post getting deleted.