The tag daf-yomi has been used most of the time for questions about the concept. For example:
Looking for daf yomi app recommendations
Preparing to learn daf yomi Yerushalmi
Daf Yomi Scheduling for Shabbos, Yom Tov, and Sundays
On the other hand, it was also used for a question on the actual daf:
Kohanim on first shift can't say Shema'?
Which is the intended purpose of the tag?