[range.concat.overview]

CPO remove and views::all(Es...) is a well formed expression
Example uses std::print in a loop

[range.concat.view]

p.4. change concat-is-bidirectional to match style of concat-is-random-access
p.7 Use pack indexing

[range.concat.iterator]

All get to std::get
All std::size_t to size_t
Remove p.29 Precondition. (and renumbering the rest)
P30/32 (new 29/31): make temp copy
P34/36 (new 33/35): "for every integer" change
P37/P39 (new 36/38): "requires changes for i - default_sentinel"