I just saw that python is listed as a dependency in the coreboot_util.sh script, but python is not an available package. See
$ apt list python
Listing... Done
$ apt list python2
Listing... Done
python2/byzantium 2.7.18-3 amd64
$ apt list python3
Listing... Done
python3/byzantium,now 3.9.2-3 amd64 [installed,automatic]