Sigma and Tamron have issued a lens compatibility notice for their lenses when used with the new Canon EOS R ($2,299 at Amazon, B&H, Adorama) full frame mirrorless camera.

There are no known issues with general operation with Sigma and Tamron lenses when used with Canon full frame mirrorless camera. But Sigma do state that the Digital Lens Optimizer located within the in-camera Lens Aberration Correction function cannot be used and must be set to Off. This will be fixed by Sigma in a future firmware update.
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https://www.dailycameranews.com/2018/10/sigma-and-tamron-lens-compatibility-notice-for-canon-eos-r/