How do I render a table with a checkbox on each row?
The form element type "tableselect" is available in Drupal 8


  Description: A table created with a far left column of radios or
  checkboxes. Build the table headings and columns with the #headers
  property, and the rows with the #options property.


https://api.drupal.org/api/drupal/developer%21topics%21forms_api_reference.html/8#tableselect

More info on "Adding checkboxes to a table" can be found in the handbook documentation here: https://www.drupal.org/node/945102