How to recover files from an unrecognised external hard drive on MacBook Pro?

Did you use macOS Disk Utility to erase this drive, or did it arrive from the factory with exFAT, or did you partition/format it using Windows?

What has changed to the system and the external drive since the last time you were able to successfully access this drive?

Do you need to share these files with Windows or are you only using this drive with macOS?

I would suggest using Disk utility to erase the whole physical drive as GUID partition and exFAT if you want to use the drive with both macOS & Windows. Other systems may format the exFAT file system using file allocation sizes that may not be compatible with macOS which appears may be the case here with the error message you posted originally.

If you are only using this drive with Macs, then erase the whole physical drive as GUID partition and either the MacOS Extended (Journaled) file system if it is a hard drive or will also be used by older versions of macOS 10.6-10.12. Or use APFS (top option) for the file system if it is an SSD and/or it will only be used by macOS 10.13+ systems.

Within Disk Utility you may need to first click "View" and select "Show All Devices" before the physical drives appear on the left pane of Disk Utility.

FYI, it is usually a good idea to erase any drive you acquire even if it appears to have an empty file system on it. Some new drives may ship with a hidden partition or software on them, plus it is a good way to make sure the file system will work properly with a Mac like in this case here.

Just make sure to temporarily move any files from this drive before erasing the drive since erasing the drive will destroy all data on it. Or you can restore from a backup. FYI, even external media needs to be backed up frequently if you have important & unique data on it.

Exact same issue: Cluster chain for /.Spotlight-V100/Store-XXXXXXXX.indexGroups has too many clusters for its size.

Did you find a solution for this? I'm having the same issue on my M1.

Did your Mac ship from the factory with an older major version of macOS such as Ventura?

Do you have access to another Mac running macOS 13.x or earlier?

Or a Windows PC?

More than likely you would need a Windows PC to retrieve those files since I'm doubtful even an older version of macOS will be able to access them, unless of course the issue is due to the Sonoma exFAT driver changes. If you have an older non-USB-C Mac, or Windows PC, but they cannot boot due to bad drives or operating systems, then you could create & use a bootable Knoppix USB stick to boot that older system to attempt to retrieve the data from the exFAT drive. Both Windows & Linux tend to be able to do things even if there are some hardware/software issues. Just let me know.

I had a similar problem with my exFAT drive. It was only after I formated the drive with a 4 kilobyte cluster size instead of the default 128 kilobyte size (too wasteful of space). I don't really know what's going on here, but I think maybe the OS wasn't updated of the fact that this was a different cluster size, and cuased translation issues. Since you're using it only with a mac, I would format your drive as APFS. Much more security features and has more redundancy in case of SSD failure or rapid unscheduled unmounting.

What file system is on this drive?

And what version of macOS are you using?

Is this a standard data drive, or is it a Time Machine backup drive?