I looked at this recently as a test. I got some test files from the Arri site and it all worked well.
I lifted this extract directly from my notes at the time:
TLDR - I got some test files from Arri and they worked fine for me on Flame 2023.3
I usually dismiss ARRIRAW outright. It is a very heavy format and may seem excessive for commercial work with tight schedules and small budgets, but the High Density Encoding (HDE) format seems like a good compromise.
HDE provides a bit-exact data reduction of uncompressed camera ARRIRAW files through encoding. With HDE, the overall storage size of RAW images can be reduced by up to a 2:1 ratio.
HDE stands for High Density Encoding, and it is an encoding technique optimized for Bayer pattern images. ARRIRAW images encoded with HDE are approximately 60% of the original size. Importantly, HDE encoding is completely lossless - when an HDE file is decoded, it perfectly matches the original file bit-for-bit.
There are two options to convert ALEXA 35 ARRIRAW MXF files to HDE MXF files; the ARRIRAW HDE Transcoder or CODEX Device Manager 7.0 and later.