I use TimeMachine (macOS proprietary backup) and my vault is stored on Obsidian folder in iCloud (so that I can access trough my iPhone and iPad. My time machine always backed up the whole iCloud Drive folder, hence also my vault.
But since I updated to sonoma that’s no longer the case, only my files inside icloud are being backed up, all app-specific files, and hence obsidian folder, are not being backed up anymore.
I didn’t know about those particular changes in Sonoma, but it makes little difference to me as I use FreeFileSync to back up multiple folders and files in one go to one or more external storage devices.
It looks complicated if you’re new to it, but doesn’t take very long to learn