Help me pick out a Linux for my friend

My friend has an ailing Chromebook and I'm getting them a decent real laptop that I'm going to put Linux on. They essentially do everything in a browser already so software compatibility isn't an issue. I'm looking for distros with high stability, KDE, unobtrusive updates that happen without user input, and a snapshot system so we can roll back if anything gets fucked up.

Also, recs for office software to get them off Google Docs (needs to be compatible with MSOffice formats)