I have set up slack alerts to a particular channel which are working, however the alerts are coming through twice. Once as the metabase user as an image, and another as a link to the question with the result from MetaBot. See below.
Hi @TimH_Euc
Metabase needs to store the images somewhere. That's what the metabase_files channel is supposed to be used for. It is not a channel you (or humans) should otherwise use.
I had the channel setup from the previous install, but when I added the new Slack App I incorrectly chose a different channel. Problem solved, thanks @flamber