Preorders:
EOS-R5 at BHphoto, Adorama.
EOS-R6 and all other new lenses can be preorder on that special page at BHphoto and Adorama.
Reviews and hands-on:
R5 Early hands-on at Dpreview. R6 early hands-in at Dpreview. Hands-on at Explora.
Videos:
Full coverage at CanonWatch.com