The 8.2 site is using System.Boolean CMS.Newsletters.SubscriberNewsletterInfo.SubscriptionEnabled in some custom code.
I'm confused as to what the question is.... If you are upgrading from 8 to 9, use the API change tool here on the devnet to find the replacement
SubscriptionEnabled property has been removed. You need to use Service<ISubscriptionService>.Entry().IsUnsubscribed method. See there about changes
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