Do you need a security clearance for most jobs?

I was wondering, how many jobs in digital forensics require a security clearance? Like 50% or less or more approximately?

I'm mainly wondering if it's possible to get a decent forensics examiner job if you're not eligible for a security clearance. I have multiple disqualifiers that'd make getting a clearance difficult, though not impossible, but just want to know if it's still a realistic career choice if you can't get a clearance.

And to clarify, I'm solely interested in just …

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