> As a side note, I don't think I ever ran into a syntax error for a system configuration file, because I couldn't figure out the format
I remember struggling to get some open source VPN package to work right. I swear I've read through the manuals three or four times but it just wouldn't work and the error messages were meaningless. I know most of the obscure formats now out of experience, but it's still not great. DNS BIND configuration and zones (and the accompanying AppArmor configuration) also caused me more trouble than necessary. Configuring and debugging inetd configuration was also something I never hope to do again.
> Well there is "man fstab", "man 5 cron" etc
Of course there is, but those aren't exactly light reading. It's not that the formats are difficult to find, it's that there's no consistency to the formats themselves with nameless columns that you need to figure out by reading several paragraphs of text.
> Which program saves configuration inside ~.local? I'm not aware of any and they generally should not. Also adding adding snap to that list is a bit besides the point, I don't think containers typically save their configuration in the registry either?
In my ~/.local/etc I see fish and bash_completion.d, for example. I don't know what programs created those, but they're there. I see some PipeWire files in ~/.local/state. ~/.local/share contains many files ending in ".conf" (most of them Flatpak, but also Kodi and GnuPG). I prefer them stuffing their config in .local rather than ignoring XDG, though. IMO Snap fits the list perfectly because it's not sold as "containers", it's sold as an "app store" even though it's focused on GUI containers. And I'm still mad about Snap not even bothering to use a capital letter in their home directory name.
I like dconf in that most settings are actually documented in context. They're searchable, use a standard format, and have structure. The ability to distinguish default values from custom settings is also very nice. IMO it's the Windows Registry but with a good editor and an even worse API.
> So how do you know what registry keys to change to achieve a certain configuration
Most of the time, I can use the find tool to find exactly what I need in the registry. I barely need to touch it anyway since most Windows settings are configurable from the GUI. Sure, it's certainly not the best config management system, but it's design is much better than the hodgepodge of configuration files unrelated systems use.
I admit that on disk, the Windows registry format is atrocious. However, the concept of a single, unified, backuppable, remotely manageable configuration system is just much better than "let's stuff some files in /etc and let people find out by making them go through our docs". I don't know where to look for config files on Linux, on most Windows tools I at least know what program I need to open to edit the configuration. I'd like DConf or at least XDG to get used more often because IMO the Linux ecosystem is the worst of two options.