(In reply to Hamish Willee from comment #9)
I've started docs for this in on MDN content and Browser compatibility.
Currently this covers making
This also mentions that you added "better extension support". What does that mean for an extension developer? What else can they do/where are you expecting docs?
"ftp" has been added to protocol_handlers, see list for
protocol at https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/manifest.json/protocol_handlers
In https://bugzilla.mozilla.org/show_bug.cgi?id=1626365#c2 you mention all these things which might change - did they, and if so how? For example can we still bookmark an FTP URL. If nothing has changed I'll leave the docs alone.
It may be able to be bookmarked, but would no longer load in Firefox.
browserSettings.ftpProtocolEnabled - will be removed or deprecated?
Setting the value is removed, but addons can still read the value.
Proxy.settings as an FTP property - will be removed or deprecated?
tabs.executeScript() notes that you can inject code from an FTP source - Remove?
proxy.register() (deprecated) notes that it will be called for any FTP request - Remove?
tabs.insertCSS() notes that the CSS can be from an FTP source - Remove?
Work with the Bookmarks API notes that you can bookmark an FTP site - will still be valid?
events.UrlFilter uses an FTP address is an example of matched URLs (urlMatches) - removed to avoid confusion?
Using ftp with any of these will no longer have any effect.