Hello,
I upgraded the firmware on my RME RayDAT on Windows using the "Windows Flash Update Tool for HDSPe Series" (release 2023-01-27), everything worked as it should on Windows after a full shutdown and booting again in Windows. Alas after rebooting on Linux the card was simply not here anymore. lspci listed it, but that's all.
The snd-hdspm module wasn't even loaded. Trying to load it didn't do anything, the RayDAT still wasn't listed in /proc/asound/cards.
I tried to reinstall the modules, and even booted on a live CD, to no success.
Finally, I could have my audio card back by compiling this module : https://github.com/PhilippeBekaert/snd-hdspe ans inserting it.
Then, I followed the instructions to build it with DKMS. The RayDAT seems now fully operational on Linux (which is a Debian sid, by the way).
Only notable difference for now is that the name of the card changed so I had to reflect that in my DAW.
I don't know exactly what has gone wrong but if anyone has this problem there is this solution.