Can't Mount External Drives

It's an interesting guess, but not accurate to say that only drives formatted as Apple File System (APFS) can be read on the Mac Studio.

Macs in general and your Mac Studio in particular can read a variety of drives using MANY different formats, including MacOS Extended HFS and many different makers' formats.

However, if you used a third-party formatter such as the aforementioned SoftRaid, or drives that came from the factory with The manufacturer's Drivers on board, you may need to Re-Install those same Drivers into MacOS (not physically onto the Drives) to access that data.

Windows New Technology File System (NTFS) presents a special problem because Microsoft has said that format is Microsoft proprietary, and threatened to sue anyone who writes it without first paying them royalties. Apple can READ, but not WRITE that format natively. There are several low-cost third-party add-ons that can provide that function.

Some drive makers include complex software that simulates a Mac files system inside a NFTS Volume structure. This is nominally "save you the trouble of reformatting" (which is preferable and actually no trouble at all). These drives will not be readable until you install all the original Drivers involved to re-create that environment.

Best Practice is, and has always been, to ERASE a new Drive with Disk Utility so that MacOS "owns' the drive with its built-in MacOS Driver.

Only drives formatted with APFS will work. If you can, I would transfer the data from the SoftRAID drives to another drive before formatting the drives to APFS. Then you can put the data back on them.

Let me know if I can be of anymore assistance.

I personally have never used SoftRAID drives, and so I probably don't have the best answers for you, but there might be a driver or software that you can install that would allow you to access these drives. You could see if anything like that works for you.

Let me know if you have any success with my suggestion - sorry I couldn't be more helpful.

In general SoftRAID drives do not use the regular Disk Utility Drivers. Instead, a SoftRAID driver is installed on the drive. So those drives might show up as "Un-identifed" format type inside Disk Utility, and may not be immediately accessible when you change versions of MacOS.

Have you run SoftRAID Utility and had it check the drive(s), and update the Drivers On the Drive as needed?

If you think that is a SoftRaid issue, contact SoftRaid or OWC for further assistance.

That is great that you got that sorted out!

We sometimes hear from Users whose Macs have crashed, and they want to restore from a backup drive, bt the drive seems to be suddenly unreadable.

That backup drive may be inaccessible unless Disk Utility alone "owns" the drive, so that it can be read in Recovery mode (where no add-ons are loaded) -- without added Drivers.