Thanks a lot, @paulw2u . That helped me log in to my normal account (from which I post now). I deleted the other account.
In my case the “SAML” account is my Ubuntu alias gunnarhj@ubuntu.com. I temporarily changed my preferred Ubuntu SSO email address to that one to be able to log in to my discourse account. However, having an alias as the preferred Ubuntu SSO address - as opposed to a ‘real’ address - does not feel as a good idea. I think I’d like to change that “SAML” address in discourse instead, but it does not seem to be editable.