On Shabbat, may I go to a public lecture and look at the screen? Slides from a computer are projected onto a projection screen. The lecturer may be using a microphone. The lecture will take place whether or not you attend.
See Rabbi Torczyner's lecture on attending conferences.
If I understood and recall his lecture correctly: Generally speaking, where necessary it would be permissible — assuming that the speaker would be using the same electronic devices regardless of your presence.
(Rabbi Torczyner always starts with "ask your local synagogue rabbi for actual psak", of course.)