I am just curious: Where can i find the changelog of a snap package?
I want to know what has changed.
It depends on the snap in question. Snaps are different from Debian packages in the archive in that they're not necessarily open-source. They're just blobs of bits. As a result, there is no requirement to have a changelog. Even if it does have one, it may not be within the snap itself. Let's take a look at Nextcloud as an example for where you might find one. First of all, look at the info for the snap:
$ snap info nextcloud
name: nextcloud
summary: Nextcloud Server - A safe home for all your data
publisher: Nextcloudâś“
contact: https://github.com/nextcloud/nextcloud-snap
[...]
Visit that "contact" url and you'll find its changelog right in the root. Each tag/release also includes the changelog snippet.
However, I reiterate: this is specific to the Nextcloud snap (which I maintain). Every snap may do it differently, and the source code (and changelog) may not be available to you.