Sigma rumored to start making mirrorless lenses for Nikon Z and Canon RF mounts in 2021. According to the latest rumors, Sigma is working on Nikon Z and Canon RF mount lenses and we may see some official announcements from Sigma in 2021.

Although Canon and Nikon both Mounts are closed and not officially opened for any third-party lens manufacturers.
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https://www.dailycameranews.com/2020/12/sigma-lenses-for-z-mount-and-rf-mount-mirrorless-cameras-coming-in-2021/