Problem mounting USB ports after installing Tahoe 26.1

Macs with Apple silicon have protections against attacks from malicious USB and Thunderbolt devices.

if you are connecting device you trust, use

Settings> Privacy & Security > allow accessories to connect

Allow USB and other accessories to connect to your Mac - Apple Support

In addition to Allow USB and other accessories to connect.........

Go to Finder > Finder Settings.. > make sure that "External disks" are checked in the General and Sidebar Settings.

Please disconnect all other external drives as it will make the command line options I will present much easier since the output will only show the problem drive. Run the following command in the Terminal app after connecting the problem drive:

diskutil  list  external

Please post the results here so we can see the drive layout of that drive. Once we know the drive layout, I can provide a couple of other commands to see what may be occurring.

Ok, that is revealing. It shows a Microsoft partition which means the file system is either exFAT or NTFS. Both can cause problems with macOS since for various reasons.

For an exFAT volume, it is always best that Disk Utility on macOS is used to erase a drive as exFAT since Windows may use a file allocation size incompatible with macOS. Plus, Apple redesigned the exFAT & FAT driver a few years ago so it may still have some bugs to work out.

An NTFS volume by default on macOS can only be mounted as Read-Only unless you install a third party NTFS driver. Most external drive manufacturers who sell their drives with NTFS from the factory generally provide the software to the user. Regardless of whether you use the manufacturer's software or pay for a third party NTFS driver, you must make sure to keep that third party software updated especially when macOS is updated with a minor update patch and especially upgrading to a new major version of macOS.

Which file system is being used here? If it is NTFS, then you will either need to update the third party software to the latest version. If that does not help, then you will either need to contact the developer of that third party software, or completely uninstall that third party software so that the built-in macOS NTFS driver can be used to read that volume.

For either file system you can try using the following Terminal command to attempt to mount the volume as Read-Only. If it fails, then it may provide a bit more information about the reason why it failed (or it may not). Replace the "diskXsY" in the sample command below with the actual device identifier for that volume which you verify after connecting the drive again since it can change each time you connect the drive.

diskutil  mount  readOnly  diskXsY

If the device identifier for that volume is "disk6s2" as shown in the output above, then the command becomes:

diskutil  mount  readOnly  disk6s2

... one more thing...

Now that you know that these features are to protect you from malicious USB and Thunderbolt devices that could attack your Mac,

When offered an unknown, untrusted USB Charger, such as in the airport, say "NO THANKS!"

an addendum to HWTechs's great advice above:

NB>>> Disk numbers are Re-derived after every Restart. Be sure you KNOW what the disk number is NOW, and do not rely on your memory.

To add to @Grant's suggestion regarding configure the "Allow Accessories to Connect"......I personally prefer to set it to "Always when unlocked". It will give you the least amount of problems while still maintaining the security of the laptop by having you confirm each device. If you use the other "safe" options, then you will find devices not reconnecting after logging back in from the lock screen, and you are likely to be prompted again for the same device the next time it connects. I have even tried the new default option Tahoe uses, and that default option has issues as well. "Always when unlocked" is the most useful & safe option to select IMHO.