I believe the CCC warning is related to the Legacy Bootable feature. The normal backup works fine in Sequoia.
CCC's legacy works fine with Intel Macs but not with Silicon Macs. The following is what Rob of Bombich Software told me as a way to clone my internal boot drive on a Silicon Mac to an external SSD:
1 - Boot into Recovery Mode
2 - Erase the external disk in Disk Utility
3 - Install macOS on the external disk
4 - When the installation has completed, accept the offer to migrate data from your original source disk
It worked like a charm and I use it to run beta Sequoia updates.
Until Apple fixes the replicator in Sequoia We'll have to clone as above.
