We shall use pre_get_posts to filter the posts of a Repeater that has been set to show 5 entries of a project CPT when viewing singular pages of the CPT such that
only the ones in the same custom taxonomy, project_category as the current entry appear AND
the current entry being viewed is not included.
Step 1
Create (if not present) and edit the Template that applies to your CPT's singular view.
Below the Inner Content component that shows your entry's content, add a Repeater having this manual query: