User documentation
You need community support for some of these.
Documentation is absolutely necessary, but many maintainers and coders hate writing it. For the major names, you have great documentation thanks to big organisations. Canonical has the Gnome version of Ubuntu, so you will find a lot on their website. Gnome also has a great site that is split between users, administrators and developers.
The KDE website also has everything covered, with a different design but great content.
To find any help about Cinnamon, start from the Linux Mint webpage – there are numerous PDF documents available. Development happens on Github. You can find most information on the spices page. if you want to make extensions, find links at https://github.com/linuxmint/cinnamon/wiki. Just like in Gnome, extensions are written in Javascript.
At first glance, the Awesome’s webpage has a link to the man page, and that is it. Look again and you see not just the libraries described one function at a time, but also an introduction to the configuration file. If you want to make your own theme tweaks and widgets, start here: https://awesomewm.org/recipes. There are many widgets here that are well documented. Most readers should understand it easily from this. Learning the Lua programming language is not necessary, since it is a very simple use of the language.
For help with Regolith, the distribution page is great. For more advanced stuff, look for i3 documentation. There are loads of videos and pages where people show off their desktops. There is a great documentation page at https://regolith-linux.org/docs/ customize/components, where you can find packages you need.