Thank you for your response. The new server is a brand new mattermost installation, I am not trying to merge two servers.
I have considered deleting all the tables on the new server, but did not know the potential [future] risks related to that… (Also, if I went that route, I would be unsure which tables not to delete, etc.).
My assumption is that there is a postgres command that would overwrite the tables on the target instance. [But I’ve had trouble finding the right postgres command(s) to do that.]
Thank you again! 