In all three, you commit your changes to Github and then let Netlify take a build and publish your content.
All of these generate backlinks when you publish. However, none of the above solutions were built keeping Obsidian in mind.
Gatsby Digital Garden was built to import and publish content from Roam. It also has a graph view. It displays transcluded text in backlinks when content is imported from Roam but not when content is authored elsewhere in markdown.
Simply Jekyll uses [[ ]] for wiki like links, and therefore can be used for publishing content authored in Obsidian. However, it also uses [[ ]] for many of its other nifty functionalities. So, you have to either let go of those functionalities or stop using Obsidian as the text editor. VS Code with Notecomplete plugin works. It is also the only one that has search built in. Check out https://www.raghuveer.net, personal blog site of the author of Simply Jekyll.
Gatsby Theme Brain does not provide either a graph view or even a list of topic. Also, it picks up topic title from the YAML frontmatter.
None of these currently support [[Actual Topic Title|Desired Display Text]] or [[Topic Title#Heading]] links. And I am not sure if any of these can be used to selectively publish topics.
I just discovered a Git-based wiki static site generator, which seems to support [[]] links https://github.com/gollum/gollum/wiki#link-tag, an RSS feed of changes to the wiki https://github.com/gollum/gollum/wiki/5.0-release-notes#rss-feed, and many more features. I wonder if folks hosting their Obsidian vault in Git would be able to use this alongside it for an easy automatic publishing solution. The RSS feed is of particular interest to me because it means I could also make a newsletter out of it. Anyone more technical than me know if there’s a reason this wouldn’t work?
This is not exact solution to your query, but look forward to this potential solution:
I recently found Publii. It is an offline CMS (static site generator). But currently don’t support any of the Obsidian features (except markdown input). However, they say they are going to allow extending it through ‘Plugins’.
Hope, it will help us publish Obsidian Vaults through it. Btw, I raised an issue for this specific enhancement on their Github profile. It would be nice if more persons, encourage them to bring such plugin.
Unfortunately, GitHub Pages still only use the same old list of plugins that are allowed, and any plugins (like simply-jekyll) are disabled for GH Pages.
Netlify is definitely the go-to option I hear from people who want to use Obsidian for publishing.