Joe Rossignol has an excellent piece at MacRumors on the saga of Linus Sebastian’s iMac Pro that Apple has declined to repair:

After the repair was declined by Apple, Sebastian and his team contacted an Apple Authorized Service Provider in Canada, where they are located. The repair shop also declined the repair, but their reason was allegedly that Apple has yet to offer the required certification courses to service the iMac Pro.

However, Apple’s internal iMac Pro Service Readiness Guide obtained by MacRumors states that ATLAS online training and learning resources for servicing the iMac Pro have been available in English since December. We also spoke to multiple sources who completed the course and received certification months ago.

The guide adds that iMac Pro service parts availability began in early to mid January, with replacement logic boards, flash storage, and memory available by late February. Multiple sources at Apple Authorized Service Providers also confirmed that iMac Pro displays are available with two-week-or-less delivery estimates.

MacRumors contacted a reliable source who confirmed that Apple Authorized Service Providers are permitted to deny service for any product that has been opened or modified by a customer, regardless of warranty, both for safety reasons and to avoid responsibility if the machine cannot be fixed.