No, you should not post on LinkedIn on behalf of someone else without their permission and without using their access details. Doing so would be considered a violation of LinkedIn's terms of service and could lead to serious consequences, including account suspension or legal issues.
LinkedIn, like most social media platforms, has specific rules and guidelines about account ownership and usage. Each user is responsible for the content they share on their own account. Impersonating someone else or posting on behalf of someone without their consent is a breach of trust and privacy.
If you want to share content or post updates on behalf of someone else, you should always seek their permission first. If they agree, they can provide you with access to their account or use LinkedIn's built-in features like "Publishing as" or "Company Page Admin" to allow you to publish on their behalf with proper authorization.
Remember, respecting other people's privacy and obtaining their consent is essential when it comes to using social media platforms or any online service on their behalf. Always follow ethical practices and adhere to the platform's terms of service to maintain trust and integrity in your online interactions.