Token API returns: `error: 'unsupported_grant_type'`

I’m sending this request:

https://www.patreon.com/api/oauth2/token?
      client_id=<secret>
      &client_secret=<secret>
      &grant_type=password
      &code=<secret>
      &username=<secret>
      &password=<secret>
      &scope=identity%20campaigns%20campaigns.members%20w:campaigns.webhook%20identity.memberships

But I’m getting 400 response: data: { error: 'unsupported_grant_type' }.

Did something changed?

UPDATE:
Sooo, there is actually a “Creator’s Access Token” now in the “Clients & API Keys” page:

It looks like I finally don’t need to fetch a new token for every request.

I’m again super concerned about the lack of communication - no warning about deprecating existing API and no help resolving the issue.

There was a hiccup with that endpoint some time ago, so it was likely that. Also do _POST instead of _GET