Go to this link:
https://www.thunderbird.net/en-US/thunderbird/60.0beta/releasenotes/
On right side : ‘Try Thunderbird Beta’
The download link takes you here:
which has the current 52.8.0 download.
The download should take you here:
So you can get to the Beta 60 download.
Thanks for reporting this. I confirm the error
I’ve opened a bug and am looking into this:
It appears as though the release notes template is used for both stable and beta versions of Thunderbird, so some logic needs to be added so that it can determine what channel’s release notes you are viewing.
As per the bug, this has been fixed. Should see the fix land by tomorrow at the latest.