A classroom poll has to work the moment you paste a link on the board. There is no time to make thirty accounts, and there is no reason to collect a single student's personal data to ask which answer they picked.
PollMaker.ai needs no signup to vote, stores no IP addresses, and includes captcha and duplicate-vote protection for free. The free tier handles up to 100 participants, which covers a lecture hall, not just a seminar.
Hand-raising over-reports the confident and under-reports everyone else. An anonymous poll gets you the distribution you actually have, which is the whole point of checking understanding before you move on.
Results can be set to appear immediately or only after the poll closes, so an early tally does not sway later voters.