I've successfully set up this account in Ubuntu using Geary, so I'm confident I've configured IMAP and my app password correctly in Google. Especially since its not failing on IMAP but explicitly on SMTP, "SMTP verification failed: could not log in. Please verify your credentials." I've tried using another app password for the SMTP credentials, but no cigar, as Google's app password manager only says the IMAP password has been used.
This is a school account hosted in gsuite, so my address doesn't end with @gmail.com, although it is still configured with imap.gmail.com and smtp.gmail.com.