It looks like there’s a bug in the LinkedIn node.
There are already GitHub issues tracking this:
- LinkedIn API out of date · Issue #14670 · n8n-io/n8n · GitHub
- n8n Linkedin node · Issue #14678 · n8n-io/n8n · GitHub
Until this is resolved, you can still use the HTTP node to make a LinkedIn post. Here’s a simple workflow — feel free to edit it to suit your needs.