https://thenextweb.com/apple/2018/11/13/apple-confirms-its-t2-chip-will-block-some-third-party-repairs/

Apple confirmed yesterday that its new security chip T2 – which it uses in MacBooks launched this year – will prevent third-party repairs to some degree.

Responding to a query from The Verge, the company verified that parts like the logic board and Touch ID components for the new Macbooks can’t be replaced by a third-party repair shop – and so you’ll have to visit an authorized Apple service center to get your laptops fixed. However, it didn’t confirm if this extends to last year’s iMac Pro – the T2 chip’s first host.