Can you bypass MailChimp's Omnivore?

Not always. Omnivore is MailChimp's AI that detects bought or scraped email lists. You shouldn't use these types of lists. Even if you've verified the emails, and even if they are all perfectly valid emails, if they look similar to something Omnivore has seen then you won't be able to upload the list to MailChimp. You're better off not using these lists or finding another email service provider.