As expected, an Atomos Ninja V firmware update will allow Canon R5C owners to record externally in Apple's ProRes RAW format. The firmware released this morning.
While the update is free, unlocking the ProRes RAW feature will require a registration via Atomos's website.
That feature allows ProRes recording in 6K resolution (at framerates ranging from 23.98p to 29.97p) and 3K (from 23.98p through 59.94p).
Full release notes can be found here.
That does not mean it is in any way an equal partnership.
Atomos have not charged extra fees for raw on R5 or any other camera that I'm aware of. I believe there is a fee for H265 recording upgrade but not raw.