In Sonoma, the setting for selecting your default web browser is in the Widgets section of the Desktop and Dock settings. Does that make any sense?
Also, even though the panel is called Desktop and Dock settings, the Dock settings are listed first.
Bit the bullet and updated to Sonoma today. Not without issues but nothing too major:
Wallpaper over-ridden - no idea why but my custom wallpaper was replaced
Find any File hung - updated to new version and it now works but is very slow to stop mid-search.
All Desktop and Document folders (iCloud) showing they need to be re-downloaded/re-synced. This took a while.
Mail search not working despite working fine in browser interface. Booted into safe mode, then back into normal boot and normal operation resumed.
Could not log into Threads - kept rejecting credentials - even directly from logged in Instagram account. The safe reboot fixed this also.
That’s all I’ve noticed for now. I thought I’d like the click on the desktop thing but it’s a little weird the way things disappear unexpectedly.