Use Siteimprove or another browser extension with support for checking duplicate IDs and mark any situations where id values repeat more than once on a single page. This issue can be fully reliant on automated tools with no manual assessment.
Siteimprove may be the easiest method as it will list out all the pages containing the error. If you find that multiple pages present the same duplicate id, make note of that in reporting instead of just saying that all 'x' number of pages have id values that repeat.
Note: This check used to be part of 4.1.1 Parsing. The success criterion 4.1.1 Parsing is deprecated in WCAG 2.2.
