Solved: Clone wouldn't boot (Intel Macbook Pro, Samsung external SSD)
 

I'm posting to thank Dave for helping me solve this.

TL;DR SamsungSSD KEXT had to be deleted off the source volume, because it prevented the copy from being bootable.

New Samsung external SSD T7. Macbook Pro 2017 (Intel) source.

Formatted the SSD to APFS (non case sensitive).

After SD clone (erase then copy) the new copy volume won't boot. Symptom: get the progress bar (no apple logo) halfway, then after a few minutes it times out and reboots to the internal drive. The SD log file shows nothing unusual, successful copy, can read all the files on the copy.

Debug: Install fresh copy of Ventura on the SSD from the OS full installer. Boots fine. Conclusion, SSD is OK and compatible.

Attempt safe boot from the copy, success. Diagnosis: probable incompatible system extension (KEXT). Check /Library/Extensions. Find they are all old except the SamsungSSD just installed after purchase of the SSD. Delete and reboots just fine.

Fix: delete the KEXT off the source, also purge the Staged Extensions using sudo kextcache --clear-staging
Clears the Staged Extensions. They can’t be manually deleted unless by root, admin is not enough.

After this: the copy no longer contains the offending KEXT and boots just fine. Proceed as normal.

Thanks Dave for helping me debug and find the issue.