Many people are attached to ideas, concepts and knowledge. So, that is also attachement to dhamma rūpa.
So, there can be taṇhā (attachement to Buddha dhamma for example) and upādāna (keeping dhamma close in mind).
Saḷāyatana might mean using sense faculties for seeking Dhamma and Buddha. One might be deliberately using ears to search for and hear dhamma sermons or might search for dhamma related books through eyes.
I heard the sermon, this is what I understand.
Lal can comment based on sinhala audio and subtitles.