Dropping this from the saved dashboard should be easy (for someone who knows how to edit these things). Does this mean we can also drop it from our logging channels in InitialiseSettings.php?

I have no idea- you should ask whoever did the change on mediawiki. Also do you really want to delete and not replace it by the others?

If they have their own channels & dashboards, not necessarily...the slow queries & such are mostly noise (to me, in this dashboard) so I don't really want those back...

My suggestion would be to substitute "channel:wfLogDBError" with a filter (out) of "lost connection to X, reconecting" and "Read timeout is reached" which are the ones that are created when there are long running queries, leaving in only real bad or illegal queries (e.g. queries that have syntax errors such as T189191).

The average rate of those in the last week is 20 errors every 3 hours, and I don't see anything there that shouldn't be fixed (aka spam).

DB replication and DBconnection could be left out as they create a lot of spam when a single server is down, or behind on replication, but mediawiki should not have a problem with that.

I can create such a filter for you, and revert it if you do not like it. I am ok if you do not want anything of that, in which case, we should remove the reference to an inexistent channel.

@greg I think I need your input here, this is the second time bugs are potentially gone unnoticed because this bug on monitoring filters. While I understand log spam is a concern, I think I can make it work with my suggestions at T165675#4040272, but I don't want to touch anything without RelEng consensus.