I have just discovered that the M1 Pegasus driver (v6.2.16) is now available for download on the Promise support page.
Or you can download it from this link...
Please read the install guide. Big Sur has security features that must be modified.
Enable System Extensions
M1 Mac running macOS 11 or later requires a one-time change to the Boot Policy before you install
the Promise Pegasus Driver. Follow the instruction in this section if the Boot Policy setting has not
yet been changed. First check to see if the Boot Policy needs to be changed