Because you are screening applicants who apply through LinkedIn, we apply the Internet Applicant Rule at this point. So, you would need to track all applicants who meet the minimum qualifications, whether or not you "speak" to them. From OFCCP's perspective, this is the first tier of evaluation. If you require all LinkedIn applicants to go through the ATS, this would be the second tier of evaluation.
You can use this OFCCP audit checklist to ensure you're doing what is required to maintain OFCCP's regulations including VEVRAA, Section 503, and EO 11246. Or request a demo to streamline your compliance and recruiting efforts.