Q. (Re- above question) can one do tashlich via zoom, during the Aseret Yemei Teshuva in case of need.
A. Horav Shlomo Miller’s Shlit’a opinion is that one should not. The reason is that reciting tashlich next
to a body of flowing water is similar to other mitzvos, where the presence of the article, place or situation that brings about a blessing or tefilah, has to be real. After all one recites a brocho only on real lightning or thunder, kiddush levana only on actually seeing the moon and not a picture or reflection or listening to the megila and answering keddusha or kaddish only when the voices are real and present.
A similar shaila that wasn’t published due to its inherent comic nature, dealt with reciting kapparot by one fellow focusing his cell phone camera on a live chicken, while his friend receives on his cell that image and proceeds to swivel the phone around his head, reciting the words of kapparot.
Rabbi A. Bartfeld as advised by Horav Shlomo Miller and Horav Aharon Miller Shlit’a