The issue is when you don’t have an account, it’s quite difficult… For someone who doesn’t know where to look for. Let’s see how we can bypass their “Join LinkedIn or Sign in” message.
First, you need to find the profile of the user targeted. Any search engine should do the trick. Usually, it’s something like :

https://www.linkedin.com/in/username

Copy that URI, and paste it to … wait for it … A Google website. The address is : http://search.google.com/test/mobile-friendly. It’s a page to test if your website is mobile friendly 😂.
Hit the test button, wait a bit, and then click on View tested page.
Copy all the HTML, and paste it to https://codebeautify.org/htmlviewer, and hit the RUN button. Now, you should be able to see more information on that profile.
Of course, if you prefer you can copy/paste the HTML code in a text file. Rename it with the .html extension before opening it with your browser.

Reproduced most of the original note above just in case of linkrot.