> can't create a new team without having provisioned a per-user key
According to the docs (https://keybase.io/docs/teams/puk) it should have automatically been created for me, though? Not sure if relevant but I did not use the auto-updater to update Keybase for macOS (if there is one), I just downloaded the latest DMG.
In turn, all team crypto operations happen for PUKs (and not device keys) so it's necessary to have a PUK before you can use teams. These details are mainly hidden from users, except for bugs (as above, but we'll fix it soon). This is a change from previous designs, but the advantage is that when a user adds a new device, she'll get instant access to all teams, when the PUK's secret key is encrypted for the new device. Whenever a user deletes a device, there's a rekey cascade --- the user's PUK is rotated, and so are all teams the user is a member of.
More info here: https://keybase.io/docs/teams/puk