Oops, I need to pull an Emily Litella, and say never mind.
What's happening is that in spite of having left the login method as 'none', Libera is recognizing that I connected using a certificate whose fingerprint is attached to my nickserv account, so nickserv is logging me into my nickserv account after login. Once I changed the login method to 'SASL EXTERNAL (/CAP)' i'm seeing the 900 and 903 messages.
