Just curious, how do remote workers onboard with their company?

And I guess basically now all offices are closed, what happens after your hired, your first day of work?

At my company to work remotely, you would need a token card and access permissions.

For our company:

Laptop preference collected a week before your start date, laptop shipped via courier to arrive on your start date. Any sensitive materials such as fobs or tags shipped separately. Phone call scheduled with manager on the morning of the first day where he'll explain the rest of the process, and a bunch of meetings then scheduled with the relevant parties to get you set up with VPN, Jira / bitbucket access, etc.

The boring but necessary HR stuff usually comes in the afternoon of the first day, then by day 2 everything should pretty much be good to go.

From there it's more standard onboarding in terms of meeting the team, joining the scrum ceremonies to listen in and take some small tasks, then progress from there.