There are several Methods for this - search for OTA... One of our STB models are still using OTA via DVB-C (I’m in Denmark). Only without the the last few months are we replacing the QAM based SWUPDATE mechanism to an TCP/IP based mechanism (IP is required for using the STB in the first place even though it’s a DVB-C BOX)

EDIT Here are the standards you want to read: https://dvb.org/?standard=specification-for-system-software-...