As far as I know 2FA is required for access groups. If it’s not possible for this person to enable GitHub 2FA, I’m afraid this won’t work.
I don’t know about the reasons why it’s not possible for this person, but would a Firefox Account be possible? As FxA supports 2FA as well, this would work as well.
MFA/2FA is a security requirement for access groups and access to NDA’d data. Firefox Account would work if 2FA is enabled for example (GitHub would also be fine, with 2FA enabled)
Also Staff is required to use 2FA on Slack: We have to use LDAP+Duo MFA.
2FA is important, that’s why we also require it from Volunteers accessing Mozilla’s Slack.
Can you share the reasons why 2FA would not work out for that particular user?