Is attending public lectures (and looking at the screen) permissible on the Sabbat? Information from a computer is projected onto a movie screen and the lecturer may be using a microphone. The lectures take place in any event.
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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.)