It's complicated...! I initially designed for any AM5, but as I started testing, and having put a cooler mounting screw into my motherboard (because they're too long) I changed the design.
For the first change I made a thicker bracket, which fixed the screws going into the mobo but needed a copper shim (a 'hat') for the CPU. I tested this for a while but was never happy with it: the design worked but the copper part was difficult to get produced to the required accuracy, so wasn't anything anyone else was going to get made (it took a lot of attempts, and quotes from some machining companies were thousands for a one-off).
Eventually I opted for custom mounting posts for the cooler, adopting the AM5 bolt pattern but replacing the cooler's fittings completely, and since I no longer used the cooler's own screws I changed the pitch for something more appropriate, losing compatibility with any AM5 cooler.
Short version: it works with any SecuFirm2 Noctua air cooler, as long as the cold plate is large enough, tested with a U12S (which works perfectly); for water cooling an EK-Pro AM5 water block fits, anything else hasn't been tested. Both these solutions have large cold plates that correctly cover the POWER9.
A lot of text... all that said, I have a pile of spares and test parts, most of which will fit any AM5 cooler, along with the custom copper part to adapt any cold plate. PM me, I've been offering to send these to anyone who asks, they're only getting recycled otherwise.