*WARINING: LOSS OF DATA MAY RESULT FROM USING THIS PRODUCT WITH BIG SUR AND TIME MACHINE
I was just informed by OWC Technical Support that SoftRaid currently does not support Time Machine when using their drivers to create a a Time Machine backup disk. This means that Time Machine backup drives using the SoftRaid drivers will no longer work properly, even if the RAID was previously working in Catalina and Time Machine will no longer properly accept (it freezes) a newly created RAID Array created with SoftRaid. Additionally, using Apple RAID Assist will eventually result in drive corruption of the drives unless the FIRMWARE of the RAIDed drives is identical. The bottom line to all of this is that the only way to reliably RAID drives in Big Sur is to use a hardware RAID solution.
Update: Support now claims to support Time Machine with SoftRAID 6.04 providing that the drives used are first formatted with APFS. SoftRAID does not support RAID and Time Machine with HFS+ formatting, the traditional format for hard disk drives.
If the drives used for the RAID array are in HFS+ (Mac Journaled) format they must be removed from the RAID array and reformatted in APFS by Apple Disk Utility, thus destroying all current data (previous Time Machine Backups) on them before using with Big Sur, SoftRAID and Time Machine.
Additionally, OWC support does not recommend using their product without having additional non-RAID’ed backups on external drives and/or off-site partially due to reliability concerns.
So, in essence, using a hardware RAID solution is still the only reliable solution for Macintosh when using Time Machine.