Tahoe 26.0.2 won't mount any external drives
Since Tahoe 26.0.2 won't mount any external drives, is it possible to revert back to iOS 15?
Question marked as
Minor point: there is no 26.0.2. There is 26, 26.0.1 and 26.1.
Finder menu > Settings > General tab, tick the box to show External Disks. Change the same setting on the Sidebar tab, if you like.
If those boxes are already checked, then open Applications > Utilities > Disk Utility, select View menu > Show all devices. Does it show up there, and if so, can you mount it?
If you have a Mac laptop computer (not applicable to Mac desktops), accessories must be allowed to connect. Go to System Settings > Privacy & Security > Accessories, try changing it to Automatically allow when unlocked or Always allow.
There were a few prior posts on this forum from users who couldn’t access their external drive due to the drive manufacturer’s software that they used to encrypt the drive. Lacie/Seagate, Samsung, SanDisk, etc., all provide 'drive management' software on their drives and using such 3rd party software can cause issues when macOS is updated and the 3rd party software becomes incompatible. Not sure if that's the issue here, but FYI the best practice with a new external drive (SSD/HDD, not applicable to NAS drives) is to use Disk Utility to complete erase it, format it as GUID/APFS and apply encryption if desired.
FWIW, I have a bunch of Samsung T7 SSDs ranging from 1 TB to 4 TB and they all work fine with my M4 Pro MacBook Pro running Tahoe.
Final note: if nothing at all is showing on your Desktop, go to System Settings > Desktop & Dock and make sure the box to Show Items On Desktop is checked.
Regarding reverting to Sequoia, it is not simple. You need to boot into Recovery OS, erase your internal drive, then install the older macOS, then restore from a backup made prior to the Tahoe upgrade. Even then, the firmware on the Mac may have been updated, meaning potential conflicts and a possible need for DFU mode and a Configurator revive/restore, which would need to be done via another Mac connected to yours. If that sounds complicated and risky, then you're assessing the situation correctly.