Heads up, you will be booking through a separate website listing their units in Airbnb. Your communications will need to be made through the Sonder customer service line, as the Airbnb messaging is a blend of automation with lightly monitoring.
Before you could check in to the unit you will need to create an account with Sonder, submit your license, additional proof of identity, phone number, and download their app so that you could be given access to the unit amenities and the check-in instructions. I was hoping to have that available the moment I reached the building, but the instructions are not available until you submit all proof of identity (which I'm worried about, because international services like these can dispose of your identity in different ways that Airbnb is expected to).
TLDR: Sonder is not related to Airbnb, and will need you to create and account, download their app, and submit proof of identity before you could enter the unit. Your host is an automated enterprise, not real people.
Personally, I'd stick with a regular Airbnb where you have access to the hosts.