As a hiring manager, I can say that not having that linkedin profile is not disqualifying, but it sure hurts your chances, a lot. Your resume must be extremely exceptional to survive the first pass if there is no linkedin profile to correlate to it. How can I know if anything is true?
I don't like it. I mean, I hate it. But when you receive 1000 resumes per day for a job posting, agressive filtering is the only way forward. My days don't have a 1000 hours.
Combine this with so many people who fabricate a fake resume with AI to sound like a perfect match to the job description. I need to review it against a linkedin job history to see if the story is consistent. Hard to believe the number of people who have their linkedin job history say one thing and their resume is completely different. This means I must be very suspicious of people who don't have a linkedin history, because it means the resume may be completely fake. So it goes to the reject pile. It's not fair, but I have 999 resumes to review after this one.
To summarize, if you are famous from conference talks, published papers or such, you don't need linkedin. If you are a regular non-famous person, you do need it.