How to immediately show group answers onscreen?
We have the Moodle online teaching tool, another is Blackboard.

On moodle one of the possible activities is "feedback" where you set the questions and make it anonymous as you wish... This may meet what you are looking for.

This does mean that all the students must get a moodle account etc.

I have seen other sites that do this interactive survey type activity but can't think of their names off-hand, but they still need the students to log-in...

A quick google search gave this article : https://www.educatorstechnology.com/2018/09/some-of-best-tools-for-creating-surveys.html

The first 4 of their list (as links can fail) Google-forms, Plickers, Kahoot and Socrative...

I use the quiz activity on moodle a lot!