Where's the best place to look for information around the release date? The page links to a MediaWiki 1.35 Branch Cut
anticipated at the beginning of August, is there anywhere else with some more up to date information, message board etc?
Topic on Talk:MediaWiki 1.35
No, this is the correct on-wiki venue; announcements to wikitech-l and mediawiki-l might be a few minutes quicker, but not much. As and when people know more, I'm sure this will be updated.
rc.0 has just been released now – https://releases.wikimedia.org/mediawiki/1.35/
Note that this is a testing pre-release, and shouldn't be used for production sites.