On an M1 Silicon computer can CCC now make a backup of the internal startup volume?
Not full bootable clone in a single step. It will make and update a clone of the Data volume, but to make that bootable you have to install the System volume onto it, or do a fresh install and migrate from the data only clone.
Once you have made it bootable CCC can update the Data volume but not the System volume. To update the system volume you have to boot to the clone and use Software Update.
All as in these two links:
https://bombich.com/kb/ccc5/creating-and-restoring-data-volume-backups
https://bombich.com/kb/ccc5/macos-big-sur-known-issues