Yes you can. We tell them we can provide a mask if they don’t have one or they can wait outside for their order and we’d be happy to bring it out to them.

Technically - yes. Officially - no, not until you have tried to offer them an alternative method (like mobile ordering from outside and you taking their order out to them, or you taking their order while they're outside like you're waiting tables).

Some SMs and DMs are supportive. Some are not.

I quit because I was being pressured to serve unmasked customers.

But heres some of what I was saying/doing as Concierge before I quit: https://www.reddit.com/r/starbucksbaristas/comments/jwvup0/barista_covid_safety_tips_tricks/?utm_medium=android_app&utm_source=share

The updated 3rd place policy allows you to refuse service to customers who ignore locate health mandates. As other have mentioned though, you have to first exhaust other options. If they refuse to meet you halfway, then you can turn them away.