Hey, I'm kind of a novice to web dev (especially when it comes to security) so could somebody please explain why you can't implement end-to-end encryption and search capability ?
You can only search data if you can read it, so it needs to be unencrypted. With end-to-end, this means only the data you have locally, so you can only do local searches. In the Slack example, (I assume) Slack uses their servers to pre-fetch search results for a faster experience.