Thanks for prompting again for clarification. I realize the documentation can be confusing but it isn’t wrong.
To explain, there are multiple versions of the webhook endpoint. The REST API v3 docs, correctly indicate only 3LO and Connect can register webhooks via POST /rest/api/3/webhook.
Meanwhile, the “Other integrations” documentation is documentation for the otherwise undocumented POST /rest/webhooks/1.0/webhook, where basic auth (via API tokens) still works. (Until today, I assumed also OAuth 1.0a.) This endpoint does not work with 3LO.
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