Great tutorial, I am about to buy a 24 bays Supermicro and I am planning how to install DSM on the new hardware. Probably I will use ESXi 6.7 and create a vm for Xpenology. I most likely will use LSI 9211-8i like you, but I guess I read somewhere that ESXi passthrough has a 16 devices limit, which got me by surprised. Looking your description, it seems you managed to passthrough all 24 disks, right?
Regarding your tutorial, should I do the same procedure every time that I upgrade DSM or just when I upgrade the boot loader?