That's not what I'm saying at all? (Edit: ah maybe I understand the confusion. I meant "to a new device and want to immediately instantly search back to the beg

That's not what I'm saying at all? (Edit: ah maybe I understand the confusion. I meant "to a new device and want to immediately instantly search back to the beginning of time" literally the way I wrote it, so if you give it a little while to download history and decrypt it upon first use then it can work the way you want from then on. /edit) Look at Wire, I can instantly search for arbitrary parts of words (no indexing going on as far as I can tell) and it returns results somewhere between instantly and a second or two depending on how far down the thousands upon thousands of messages the result is. It's end to end encrypted and doesn't use any homomorpic encryption magic (not sure if that's production-ready yet, but if it is, they don't use it here). It's all local and in a browser at that, no need for some special optimized C code either. There are definitely solutions here that support exactly what you want without requiring plaintext server access. We just need to use them.