If you want random post display you can use 'Manual' option in Repeater/Easy.

Option 1

Repeater or Easy Posts > Query > Manual

category_name=xxxxxx&posts_per_page=3

post_type-post&posts_per_page=3

post_type=post&posts_per_page=3&offset=3&no_found_rows=true

post_type=archive&posts_per_page=4&no_found_rows=true&orderby=rand

author_name=admin&category_name=catalogue&posts_per_page=4&orderby=rand

Use below code

category_name=xxxxxx&posts_per_page=3&offset=3&no_found_rows=true
or
post_type-post&posts_per_page=3&offset=3&no_found_rows=true

post_type=post&posts_per_page=3&offset=3&no_found_rows=true

post_type=archive&posts_per_page=4&no_found_rows=true&orderby=rand

author_name=admin&category_name=catalogue&posts_per_page=4&orderby=rand

If you are using ACF you can use your category, by changing as below...

post_type=post&posts_per_page=3&offset=3&no_found_rows=true

Option 2

To create Random post go to Repeater > Query > Advanced > Add a query like below