Yes, ecash is a bearer asset and is all stored in your browser.

Afaik nostr:npub1cj6ndx5akfazux7f0vjl4fyx9k0ulf682p437fe03a9ndwqjm0tqj886t6 is working on a backup solution specifically for Umbrel users but ecash backups are a bit finicky. We're working on a backup path with seed phrases, similar to what you know from Bitcoin.

SoonTM

Please be cautious and only use with minimal amounts! And most importantly: Praise the nut!