or via stylus
new style for feed -> paste:
[data-testid="mainFeed"]{display:none}
in full:
/* ==UserStyle==
@name www.linkedin.com/feed
@namespace github.com/openstyles/stylus
@version 1.0.0
@description A new userstyle
@author Me
==/UserStyle== */
@-moz-document url-prefix("https://www.linkedin.com/feed/")
{
[data-testid="mainFeed"]{display:none}
}