Yes it is possible to automate posting on a personal LinkedIn profile like in the video but not through the official LinkedIn API. The method shown uses browser automation through a tool like Puppeteer or Browserless that logs into your account and publishes the post as if you were doing it yourself.
This approach works with personal profiles and you can replicate it in n8n. It is an unofficial method and it depends on the LinkedIn interface so it can break if the site changes. Use it only if you understand these limitations.
I am running into troubles as i have n8n locally and then ngrok for public urls + getting redirect urls for OAuth is challenging. In your experience, is it best to use n8n in the cloud or local?