Why not an EOS R ?
For Canon, mirrorless is "the future".
It will work with all your existing EF lenses, AND work with the EF-S lenses, as well (although the images will be cropped).
If you get a mirrored Canon full-frame, it WILL NOT work with any of your EF-S lenses (I believe).
No more fooling with micro-focus adjustments, that no longer applies with mirrorless.
If you get an EOS R, pay $100 extra for the Canon lens adapter with the control ring.
It will make your existing EF lenses MORE useful with the mirrorless mount.
When shooting landscape with the EOS R, using a fairly heavy wide angle lens like the Sigma 14-24mm, how taxing is it on the camera to have all that weight extended out from the tripod mounting point of camera?
I would think all that weight being extended away with the mount adapter would make for a scary setup?
At least the EOS-M adapter had a tripod mount built in.