It looks like the man page urls changed at some point (I think in the last week or so maybe?)
At some point they were in the format: https://www.collectd.org/documentation/manpages/collectd.conf.5.shtml
But are now: https://www.collectd.org/documentation/manpages/collectd.conf.html
There are still a lot of incoming links to the old urls. Such as from the wiki: https://github.com/collectd/collectd/wiki/Plugin-Tail
I can't find a way to do proper redirects with github pages, it looks like you have to do it with a little html stub file (which looks to have been done with some old wiki pages in this repository).
It looks like the man page urls changed at some point (I think in the last week or so maybe?)
At some point they were in the format: https://www.collectd.org/documentation/manpages/collectd.conf.5.shtml
But are now: https://www.collectd.org/documentation/manpages/collectd.conf.html
There are still a lot of incoming links to the old urls. Such as from the wiki: https://github.com/collectd/collectd/wiki/Plugin-Tail
I can't find a way to do proper redirects with github pages, it looks like you have to do it with a little html stub file (which looks to have been done with some old wiki pages in this repository).